Biomedical subjects

Yan Wu

Publications and source records attributed to Yan Wu.

At least 73 records · Page 4Linked to original sources

PubMed2005

Chitosan nanoparticles as a novel delivery system for ammonium glycyrrhizinate.

The ammonium glycyrrhizinate-loaded chitosan nanoparticles were prepared by ionic gelation of chitosan with tripolyphosphate anions (TPP). The particle size and zeta potential of nanoparticles were determined, respectively, by dynamic light scattering (DLS) and a zeta potential analyzer. The effects, including chitosan molecular weight, chitosan concentration, ammonium glycyrrhizinate concentration and polyethylene glycol (PEG) on the physicochemical properties of the nanoparticles were studied. These nanoparticles have ammonium glycyrrhizinate loading efficiency. The encapsulation efficiency decreased with the increase of ammonium glycyrrhizinate concentration and chitosan concentration. The introduction of PEG can decrease significantly the positive charge of particle surface. These studies showed that chitosan can complex TPP to form stable cationic nanoparticles for subsequent ammonium glycyrrhizinate loading.

Chitosan↗

PubMed2005

Dedifferentiation of adult human myoblasts induced by ciliary neurotrophic factor in vitro.

Ciliary neurotrophic factor (CNTF) is primarily known for its important cellular effects within the nervous system. However, recent studies indicate that its receptor can be highly expressed in denervated skeletal muscle. Here, we investigated the direct effect of CNTF on skeletal myoblasts of adult human. Surprisingly, we found that CNTF induced the myogenic lineage-committed myoblasts at a clonal level to dedifferentiate into multipotent progenitor cells--they not only could proliferate for over 20 passages with the expression absence of myogenic specific factors Myf5 and MyoD, but they were also capable of differentiating into new phenotypes, mainly neurons, glial cells, smooth muscle cells, and adipocytes. These "progenitor cells" retained their myogenic memory and were capable of redifferentiating into myotubes. Furthermore, CNTF could activate the p44/p42 MAPK and down-regulate the expression of myogenic regulatory factors (MRFs). Finally, PD98059, a specific inhibitor of p44/p42 MAPK pathway, was able to abolish the effects of CNTF on both myoblast fate and MRF expression. Our results demonstrate the myogenic lineage-committed human myoblasts can dedifferentiate at a clonal level and CNTF is a novel regulator of skeletal myoblast dedifferentiation via p44/p42 MAPK pathway.

Animals↗

PubMed2005

Product release is rate-limiting in the activation of the prodrug 5-fluorocytosine by yeast cytosine deaminase.

Yeast cytosine deaminase (yCD), a zinc metalloenzyme, catalyzes the hydrolytic deamination of cytosine to uracil. The enzyme is of great biomedical interest because it also catalyzes the deamination of the prodrug 5-fluorocytosine (5FC) to form the anticancer drug 5-fluorouracil (5FU). yCD/5FC is one of the most widely used enzyme/prodrug combinations for gene-directed enzyme prodrug therapy for the treatment of cancers. A pH indicator assay has been developed for the measurement of the steady-state kinetic parameters for the deamination reaction. Transient kinetic studies have shown that the product release is a rate-limiting step in the activation of the prodrug 5FC by yCD. The rate constant of the chemical step for the forward reaction (250 s(-)(1)) is approximately 8 times that of the product release (31 s(-)(1)) and approximately 15 times k(cat) (17 s(-)(1)). The transient kinetic results are consistent with those of the steady-state kinetic analysis in the sense that the k(cat) and K(m) values calculated from the rate constants determined by the transient kinetic analysis are in close agreement with those measured by the steady-state kinetic analysis. NMR experiments have demonstrated that free 5FU is in slow exchange with its complex with yCD but has a low affinity for yCD. The transient kinetic and NMR results together suggest that the release of 5FU is rate-limiting in the activation of the prodrug 5FC by yCD and may involve multiple steps.

Antimetabolites, Antineoplastic↗

PubMed2005

Fetal stromal-dependent paracrine and intracrine vascular endothelial growth factor-a/vascular endothelial growth factor receptor-1 signaling promotes proliferation and motility of human primary myeloma cells.

Induction of neoangiogenesis plays an important role in the pathogenesis of multiple myeloma. However, the mechanism by which expression of vascular endothelial growth factor (VEGF)-A and its receptors modulate the interaction of multiple myeloma cells with stromal cells is not known. Here, we describe a novel in vitro coculture system using fetal bone stromal cells as a feeder layer, which facilitates the survival and growth of human primary multiple myeloma cells. We show that stromal-dependent paracrine VEGF-A signaling promotes proliferation of human primary multiple myeloma cells. Primary multiple myeloma cells only expressed functional VEGF receptor (VEGFR)-1, but not VEGFR-2 or VEGFR-3. VEGFR-1 expression was detected in the cytoplasm and the nuclei of proliferating multiple myeloma cells. Inhibition of VEGFR-1 abrogated multiple myeloma cell proliferation and motility, suggesting that the functional interaction of VEGF-A with its cognate receptor is essential for the growth of primary multiple myeloma cells. Collectively, our results suggest that stromal-dependent paracrine and intracrine VEGF-A/VEGFR-1 signaling contributes to human primary multiple myeloma cell growth and therefore, VEGFR-1 blockade is a potential therapeutic strategy for the treatment of multiple myeloma.

Bone and Bones↗

PubMed2005

Expression and function of vascular endothelial growth factor receptor-1 on human colorectal cancer cells.

Vascular endothelial growth factor (VEGF) is associated with tumor angiogenesis and poor prognosis in human colorectal cancer (CRC). VEGF receptor-1 (VEGFR-1 or Flt-1) is a high-affinity receptor for VEGF and is typically considered specific to endothelial cells. Here we report the expression and function of VEGFR-1 in CRC cell lines. VEGFR-1 was expressed in all CRC cell lines studied as determined by RT-PCR, Western blot analysis, FACS, and ELISA. Treatment of the human CRC cell lines HT-29 and SW480 with VEGF-A (a ligand for both VEGFR-1 and -2) or VEGF-B (a ligand specific for VEGFR-1) led to activation of Erk-1/2, SAPK/JNK, and translocation of the p65 subunit of nuclear factor-kappaB into the nucleus. Both VEGF-A and -B led to significant induction of cell motility and invasiveness of CRC cells. Stimulation of cells with VEGF-A or -B also led to larger and more numerous colonies in soft agar. However, activation of VEGFR-1 did not increase CRC cell proliferation. In contrast to the previous paradigm that VEGFRs are not present on tumor cells of epithelial origin, we found that VEGFR-1 is present and functional on CRC cells, and activation by VEGF family ligands can activate processes involved in tumor progression and metastasis.

Blotting, Western↗

PubMed2005

[The effect of carvedilol on apoptosis gene PDCD5 expression in chronic heart failure patients].

OBJECTIVE: To observe the changes of serum PDCD5 antibody in chronic ischemic heart failure patients and the effect of carvedilol treatment. METHODS: Twenty chronic ischemic heart failure patients, 11 males and 9 females, aged 58 +/- 13, with the left ventricular ejection fraction (LVEF) < 45% by echocardiography and New York Heart Association (NYHA) cardiac function classification II-III, were treated with carvedilol for 6 months with a target dosage of 50 mg/d. The serum PDCD5 antibody was tested by ELISA before and after carvedilol treatment and compared with those of 20 healthy persons. RESULTS: The A value of PDCD5 antibody in the heart failure patients was 3.5 +/- 1.4, significantly higher that in than healthy persons (1.9 +/- 1.0, P < 0.01). After treatment of carvedilol, the A value of PDCD5 antibody in the heart failure patients decreased to 2.5 +/- 1.2 (P < 0.05). In 6 months maintenance treatment, 14 (70%) patients reached the dosage 50 mg/d, 4 (20%) reached 25 mg/d, and 2 (10%) reached 12.5 mg/d. Five patients (25%) had side effect such as dizziness, nausea and cough, one patient (5%) was hospitalized for 3 weeks because of heart failure, no patient died. After treatment of carvedilol, the NYHA degree increased by 0.3 (P < 0.05), LVEF increased from 35.5% +/- 7.8% to 42.7% +/- 9.6% (P < 0.05), left ventricular end-diastolic diameter decreased 5.3 mm (P < 0.05), and left ventricular end-systolic diameter decreased by 8.1 mm (P < 0.01). CONCLUSION: The titer of apoptosis gene PDCD5 antibody in the serum of chronic ischemic heart failure patients are higher, which shows apoptosis and treatment of carvedilol significantly decreases its titer.

Adrenergic alpha-Antagonists↗

PubMed2005

Importance of cellular microenvironment and circulatory dynamics in B cell immunotherapy.

B cell immunotherapy has emerged as a mainstay in the treatment of lymphomas and autoimmune diseases. Although the microenvironment has recently been demonstrated to play critical roles in B cell homeostasis, its contribution to immunotherapy is unknown. To analyze the in vivo factors that regulate mechanisms involved in B cell immunotherapy, we used a murine model for human CD20 (hCD20) expression in which treatment of hCD20(+) mice with anti-hCD20 mAbs mimics B cell depletion observed in humans. We demonstrate in this study that factors derived from the microenvironment, including signals from the B cell-activating factor belonging to the TNF family/BLyS survival factor, integrin-regulated homeostasis, and circulatory dynamics of B cells define distinct in vivo mechanism(s) and sensitivities of cells in anti-hCD20 mAb-directed therapies. These findings provide new insights into the mechanisms of immunotherapy and define new opportunities in the treatment of cancers and autoimmune diseases.

Animals↗

PubMed2005

Complete and specific inhibition of adult lymphatic regeneration by a novel VEGFR-3 neutralizing antibody.

BACKGROUND: New lymphatic growth may contribute to tumor metastasis. Activation of vascular endothelial growth factor receptor 3 (VEGFR-3) by its ligands VEGF-C and -D is necessary for embryonic and tumor lymphangiogenesis. However, the exact role of VEGFR-3 signaling in adult lymphangiogenesis and in lymphatic vessel survival and regeneration is unclear. METHODS: A novel rat monoclonal antibody to murine VEGFR-3, mF4-31C1, which potently antagonizes the binding of VEGF-C to VEGFR-3, was developed. We tested the effects of systemic mF4-31C1 administration in a mouse tail skin model of lymphatic regeneration, either with or without local overexpression of VEGF-C, and we observed lymphatic and blood vessel regeneration over time using microlymphangiography and immunostaining. RESULTS: Normal mice regenerated complete and functional lymphatic vessels within 60 days of surgery. In athymic mice implanted with VEGF-C-overexpressing human breast carcinoma cells, lymphatic regeneration took place over 25 days and resulted in hyperplastic vessels. Under either condition, no lymphatic regeneration occurred in mice receiving mF4-31C1 during the regeneration period. Blood angiogenesis and preexisting lymphatic vessels were unaffected, both in morphology and in function. CONCLUSIONS: Blocking VEGFR-3 completely and specifically prevented both physiologically normal and tumor VEGF-C-enhanced lymphangiogenesis in the adult mouse but had no effect on either blood angiogenesis or the survival or function of existing lymphatic vessels. Thus, targeting VEGFR-3 with specific inhibitors may block new lymphatic growth exclusively.

Animals↗

PubMed2005

Paraneoplastic pemphigus associated with Castleman tumor: a commonly reported subtype of paraneoplastic pemphigus in China.

BACKGROUND: Castleman tumor, a rare lymphoproliferative disorder, is one of the associated tumors in paraneoplastic pemphigus. We analyzed the characteristics of a group of patients with Castleman tumor to clearly understand and to improve the prognosis of the disease. OBSERVATIONS: Ten cases of paraneoplastic pemphigus associated with Castleman tumor treated in the Department of Dermatology, Peking University First Hospital, Beijing, China, from May 1, 1999, to March 31, 2004, were analyzed for clinical aspects, characteristics and histologic features of the tumors, and computed tomographic findings. Literature was reviewed and data were compared with our cases. Castleman tumor was a frequently reported neoplasm in association with paraneoplastic pemphigus in China. The disease was found to be caused by an autoimmune reaction originating from the B lymphocytes in the Castleman tumor. CONCLUSIONS: Castleman tumor in association with paraneoplastic pemphigus is a commonly reported subtype of paraneoplastic pemphigus in China. Early detection and removal of the Castleman tumor are crucial for the treatment of this tumor-associated autoimmune disease.

Adolescent↗

PubMed2005

Susceptibility to vaginal candidiasis under different conditions in mice.

In order to study the susceptibility of murine vaginal mucosa to Candida albicans under different conditions, vaginal lavage fluid and vaginal tissue of mice were observed and compared between murine models with normal immune system (estrogen-treated mice) and immunosuppressed murine model, and between primary infection model of vaginal candidiasis and secondary infection one. The average level of colony forming unit (CFU) from the immuosuppressed group was higher than that from estrogen-treated group at each time point and the peak time was delayed. The differences between the two groups were statistically significant (P < 0.05) from the fourth day after inoculation. A significant difference existed in the average level of CFU between the control group and the estrogen-treated group (P < 0.05), and between the control group and the immuosuppressed group (P < 0.01). It was concluded that the vaginal mucosa from the immunosuppressed mice is more susceptible to Candida albicans and no difference is found in susceptibility between mice with primary infection and secondary infection.

Animals↗

PubMed2005

Aberrant methylation at HOXA10 may be responsible for its aberrant expression in the endometrium of patients with endometriosis.

OBJECTIVE: HOXA10, expressed in endometrium, plays an important role in uterine receptivity at the time of implantation. In the endometrium of women with endometriosis, its expression is reduced. The aim of this study was to determine whether the observed aberrant expression of HOXA10 is caused by aberrant methylation of the gene. STUDY DESIGN: Endometrial tissues were collected from 6 women with laparoscopically confirmed endometriosis, and 4 women who underwent tubal ligation and were confirmed to have no endometriosis. In addition, menstrual blood from 5 women with no gynecologic complaints was collected and also used as controls. Methylation-specific polymerase chain reaction (PCR) and bisulfite sequencing were performed in 3 fragments in 2 regions of HOXA10 to detect difference in methylation patterns. Real-time reverse transcriptase (RT)-PCR was also performed to measure expression levels of HOXA10 in select cases and controls. RESULTS: In all 3 fragments, there were highly statistically significant differences in methylation patterns between women with endometriosis and those without endometriosis. The expression level of HOXA10 was lower in women with endometriosis than those without, as previously reported. CONCLUSION: There is aberrant methylation in the endometrium of women with endometriosis compared with those without endometriosis. The aberrant methylation at HOXA10 may be responsible for the aberrant gene expression in the endometrium of women with endometriosis. This finding suggests that endometriosis may also be an epigenetic disease.

Base Sequence↗

PubMed2005

Age related changes of various markers of astrocytes in senescence-accelerated mice hippocampus.

Astrocytes play a critical role in maintaining normal brain physiology during development and in adulthood, while to date the changes of astrocytes during aging and their effects on age-related functional decline have not been well understood. This study used immunohistochemistry, western blot, and reverse transcriptase polymerase chain reaction techniques to investigate the expression of glial fibrillary acidic protein (GFAP), glutamine synthetase (GS), and S100 beta proteins and mRNAs in the hippocampi of 3 months old and 16 months old senescence-accelerated-prone mice (SAMP8) and senescence-accelerated-resistant mice (SAMR1). The results showed significant age-related increases in both protein and mRNA levels of GFAP in the hippocampi of aged SAMP8 and SAMR1. As well, the GFAP of aged SAMP8 was significantly greater than that of aged SAMR1. However, no such increase was observed for either GS or S100 beta. These results suggested that GFAP, rather than GS or S100 beta, played a more important role in the age related deficits in learning and memory.

Aging↗

PubMed2005

Ectonucleotidases of CD39 family modulate vascular inflammation and thrombosis in transplantation.

Transplantation results in exposure of the graft vasculature to warm and cold ischemia, followed by perfusion by circulating blood constituents and obligatory oxidant stress. Further graft injury occurs as consequences of acute humoral cellular rejection or chronic transplant vasculopathy, or both. Extracellular nucleotide stimulation of purinergic type 2 (P2) receptors are key components of platelet, endothelial cell (EC), and leukocyte activation resulting in vascular thrombosis and inflammation in vivo. CD39, the prototype nucleoside triphosphate diphosphohydrolase (NTPDase-1) is highly expressed on endothelium; in contrast, CD39L1/NTPDase-2 (a preferential adenosine triphosphatase [ATPase]) is found on vascular adventitial cells. Both ectoenzymes influence thrombogenesis by the regulated hydrolysis of extracellular nucleotides that differentially regulate P2-receptor activity and function in platelets and vascular cells. The intracytoplasmic domains of NTPDase-1 may also independently influence cellular activation and proliferation. NTPDase activity is substantively lost in the vasculature of injured or rejected grafts. A role for NTPDase-1 in thromboregulation has been validated by generation of mutant mice either null for cd39 or overexpressing human CD39. Administration of soluble NTPDase or induction of CD39 by adenoviral vectors, or both, are also of benefit in several models of transplantation. Administration of soluble CD39 or targeted expression may have future therapeutic application in transplantation-associated and other vascular diseases.

Adenosine Triphosphatases↗

PubMed2005

Dose sculpting with generalized equivalent uniform dose.

With intensity-modulated radiotherapy (IMRT), a variety of user-defined dose distribution can be produced using inverse planning. The generalized equivalent uniform dose (gEUD) has been used in IMRT optimization as an alternative objective function to the conventional dose-volume-based criteria. The purpose of this study was to investigate the effectiveness of gEUD optimization to fine tune the dose distributions of IMRT plans. We analyzed the effect of gEUD-based optimization parameters on plan quality. The objective was to determine whether dose distribution to selected structures could be improved using gEUD optimization without adversely altering the doses delivered to other structures, as in sculpting. We hypothesized that by carefully defining gEUD parameters (EUD0 and n) based on the current dose distributions, the optimization system could be instructed to search for alternative solutions in the neighborhood, and we could maintain the dose distributions for structures already satisfactory and improve dose for structures that need enhancement. We started with an already acceptable IMRT plan optimized with any objective function. The dose distribution was analyzed first. For structures that dose should not be changed, a higher value of n was used and EUD0 was set slightly higher/lower than the EUD value at the current dose distribution for critical structures/targets. For structures that needed improvement in dose, a higher to medium value of n was used, and EUD0 was set to the EUD value or slightly lower/higher for the critical structure/target at the current dose distribution. We evaluated this method in one clinical case each of head and neck, lung and prostate cancer. Dose volume histograms, isodose distributions, and relevant tolerance doses for critical structures were used for the assessment. We found that by adjusting gEUD optimization parameters, the dose distribution could be improved with only a few iterations. A larger value of n could lead to faster convergence and a medium value of n could result in a search in a broader area. Such improvement could also be achieved by optimization based on other criteria, but the gEUD-based method has the advantage of efficiency and flexibility. Therefore, gEUD-based optimization can be used as a tool to improve IMRT plans by adjusting the planning parameters, thereby making dose sculpting feasible.

Algorithms↗

PubMed2005

Effects of glucosinolate-rich broccoli sprouts on urinary levels of aflatoxin-DNA adducts and phenanthrene tetraols in a randomized clinical trial in He Zuo township, Qidong, People's Republic of China.

Residents of Qidong, People's Republic of China, are at high risk for development of hepatocellular carcinoma, in part due to consumption of aflatoxin-contaminated foods, and are exposed to high levels of phenanthrene, a sentinel of hydrocarbon air toxics. Cruciferous vegetables, such as broccoli, contain anticarcinogens. Glucoraphanin, the principal glucosinolate in broccoli sprouts, can be hydrolyzed by gut microflora to sulforaphane, a potent inducer of carcinogen detoxication enzymes. In a randomized, placebo-controlled chemoprevention trial, we tested whether drinking hot water infusions of 3-day-old broccoli sprouts, containing defined concentrations of glucosinolates, could alter the disposition of aflatoxin and phenanthrene. Two hundred healthy adults drank infusions containing either 400 or < 3 micromol glucoraphanin nightly for 2 weeks. Adherence to the study protocol was outstanding; no problems with safety or tolerance were noted. Urinary levels of aflatoxin-N(7)-guanine were not different between the two intervention arms (P = 0.68). However, measurement of urinary levels of dithiocarbamates (sulforaphane metabolites) indicated striking interindividual differences in bioavailability. An inverse association was observed for excretion of dithiocarbamates and aflatoxin-DNA adducts (P = 0.002; R = 0.31) in individuals receiving broccoli sprout glucosinolates. Moreover, trans, anti-phenanthrene tetraol, a metabolite of the combustion product phenanthrene, was detected in urine of all participants and showed a robust inverse association with dithiocarbamate levels (P = 0.0001; R = 0.39), although again no overall difference between intervention arms was observed (P = 0.29). Understanding factors influencing glucosinolate hydrolysis and bioavailability will be required for optimal use of broccoli sprouts in human interventions.

Adult↗

PubMed2005

Targeting the platelet-derived growth factor receptor alpha with a neutralizing human monoclonal antibody inhibits the growth of tumor xenografts: implications as a potential therapeutic target.

Platelet-derived growth factor receptor alpha (PDGFRalpha) is a type III receptor tyrosine kinase that is expressed on a variety of tumor types. A neutralizing monoclonal antibody to human PDGFRalpha, which did not cross-react with the beta form of the receptor, was generated. The fully human antibody, termed 3G3, has a Kd of 40 pmol/L and blocks both PDGF-AA and PDGF-BB ligands from binding to PDGFRalpha. In addition to blocking ligand-induced cell mitogenesis and receptor autophosphorylation, 3G3 inhibited phosphorylation of the downstream signaling molecules Akt and mitogen-activated protein kinase. This inhibition was seen in both transfected and tumor cell lines expressing PDGFRalpha. The in vivo antitumor activity of 3G3 was tested in human glioblastoma (U118) and leiomyosarcoma (SKLMS-1) xenograft tumor models in athymic nude mice. Antibody 3G3 significantly inhibited the growth of U118 (P=0.0004) and SKLMS-1 (P <0.0001) tumors relative to control. These data suggest that 3G3 may be useful for the treatment of tumors that express PDGFRalpha.

Animals↗

PubMed2005

[An overview of injectable and absorbable gelling scaffolds].

In this article, based on the relative references in the latest 8 years, we introduce briefly the origin, preparation and application of various injectable and absorbable gelling scaffold materials, and outline their advantages and disadvantages as localized gelling scaffold systems.

Absorbable Implants↗

PubMed2005

[Emission spectra of hydroxyl radical generated in air corona discharge].

In this paper, the relative emission intensity of the 309 nm transition band of hydroxyl radical (OH) was measured by a CCD imaging spectrometer in a pin-plane corona discharge scheme of one atmosphere pressure air injected with unsaturated water vapor from the central hole of the used pins. The influences of several factors on the OH radical production were investigated by relative emission intensity measurement. The production of OH radical increased with a limited increment of water vapor concentration in the mixed gas. Compared with positive DC corona discharges, more OH radicals were generated in positive pulsed corona discharges and less in negative DC corona discharges. The spatial distribution of OH radical production was also observed. Most OH radicals were produced within the range of 5 mm off the discharge pin electrode. In conclusion, this means of optical emission spectroscopy, compared with more sophisticated laser fluorescence measurements used for plasma OH production diagnostics investigation, is simpler and more effective for characterizing the OH radical potential for pollutant oxidation.

Air↗