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Yang Wang

Publications and source records attributed to Yang Wang.

At least 37 records · Page 2Linked to original sources
PubMed2006

Trans-differentiation of alveolar epithelial type II cells to type I cells involves autocrine signaling by transforming growth factor beta 1 through the Smad pathway.

Type II alveolar epithelial cells (AEC II) proliferate and transdifferentiate into type I alveolar epithelial cells (AEC I) when the normal AEC I population is damaged in the lung alveoli. We hypothesized that signaling by transforming growth factor beta1 (TGF beta1), through its downstream Smad proteins, is involved in keeping AEC II quiescent in normal cells and its altered signaling may be involved in the trans-differentiation of AEC II to AEC I. In the normal lung, TGF beta1 and Smad4 were highly expressed in AEC II. Using an in vitro cell culture model, we demonstrated that the trans-differentiation of AEC II into AEC I-like cells began with a proliferative phase, followed by a differentiation phase. The expression of TGF beta1, Smad2, and Samd3 and their phosphorylated protein forms, and cell cycle inhibitors, p15(Ink4b) and p21(Cip1), was lower during the proliferative phase but higher during the differentiation phase. Furthermore, cyclin-dependent kinases 2, 4, and 6 showed an opposite trend of expression. TGF beta1 secretion into the media increased during the differentiation phase, indicating an autocrine regulation. The addition of TGF beta1 neutralizing antibody after the proliferative phase and silencing of Smad4 by RNA interference inhibited the trans-differentiation process. In summary, our results suggest that the trans-differentiation of AEC II to AEC I is modulated by signaling through the Smad-dependent TGF beta1 pathway by altering the expression of proteins that control the G1 to S phase entry in the cell cycle.

Animals↗
PubMed2006

Bipolar electrochemical mechanism for the propulsion of catalytic nanomotors in hydrogen peroxide solutions.

Bimetallic nanorods are propelled in aqueous solutions by the catalytic decomposition of hydrogen peroxide to oxygen and water. Several mechanisms (interfacial tension gradients, bubble recoil, viscous Brownian ratchet, self-electrophoresis) have been proposed for the transduction of chemical to mechanical energy in this system. From Tafel plots of anodic and cathodic hydrogen peroxide reactions at various metal (Au, Pt, Rh, Ni, Ru, and Pd) ultramicroelectrodes, we determine the potential at which the anodic and cathodic reaction rates are equal for each metal. These measurements allow one to predict the direction of motion of all possible bimetallic combinations according to the bipolar electrochemical (or self-electrophoretic) mechanism. These predictions are consistent with the observed direction of motion in all cases studied, providing strong support for the mechanism. We also find that segmented nanorods with one Au end and one poly(pyrrole) end containing catalase, an enzyme that decomposes hydrogen peroxide nonelectrochemically, perform the overall catalytic reaction at a rate similar to that of nanorods containing Au and Pt segments. However, in this case there is no observed axial movement, again supporting the bipolar electrochemical propulsion mechanism for bimetallic nanorods.

Catalysis↗
PubMed2006

Catalytically induced electrokinetics for motors and micropumps.

We have explored the role of electrokinetics in the spontaneous motion of platinum-gold nanorods suspended in hydrogen peroxide (H2O2) solutions that may arise from the bimetallic electrochemical decomposition of H2O2. The electrochemical decomposition pathway was confirmed by measuring the steady-state short-circuit current between platinum and gold interdigitated microelectrodes (IMEs) in the presence of H2O2. The resulting ion flux from platinum to gold implies an electric field in the surrounding solution that can be estimated from Ohm's Law. This catalytically generated electric field could in principle bring about electrokinetic effects that scale with the Helmholtz-Smoluchowski equation. Accordingly, we observed a linear relationship between bimetallic rod speed and the resistivity of the bulk solution. Previous observations relating a decrease in speed to an increase in ethanol concentration can be explained in terms of a decrease in current density caused by the presence of ethanol. Furthermore, we found that the catalytically generated electric field in the solution near a Pt/Au IME in the presence of H2O2 is capable of inducing electroosmotic fluid flow that can be switched on and off externally. We demonstrate that the velocity of the fluid flow in the plane of the IME is a function of the electric field, whether catalytically generated or applied from an external current source. Our findings indicate that the motion of PtAu nanorods in H2O2 is primarily due to a catalytically induced electrokinetic phenomenon and that other mechanisms, such as those related to interfacial tension gradients, play at best a minor role.

Catalysis↗
PubMed2006

Antibiotic-conjugated polyacrylate nanoparticles: new opportunities for development of anti-MRSA agents.

This report describes the preparation of polyacrylate nanoparticles in which an N-thiolated beta-lactam antibiotic is covalently conjugated onto the polymer framework. These nanoparticles are formed in water by emulsion polymerization of an acrylated antibiotic pre-dissolved in a liquid acrylate monomer (or mixture of co-monomers) in the presence of sodium dodecyl sulfate as a surfactant and potassium persulfate as a radical initiator. Dynamic light scattering analysis and electron microscopy images of these emulsions show that the nanoparticles are approximately 40 nm in diameter. The emulsions have potent in vitro antibacterial properties against methicillin-resistant Staphylococcus aureus and have improved bioactivity relative to the non-polymerized form of the antibiotic. A unique feature of this methodology is the ability to incorporate water-insoluble drugs directly into the nanoparticle framework without the need for post-synthetic modification. Additionally, the antibiotic properties of the nanoparticles can be modulated by changing the length or location of the acrylate linker on the drug monomer.

Acrylic Resins↗
PubMed2006

Unusual hydrogen bonding in water-filled carbon nanotubes.

We present the first experimental vibrational spectroscopy study providing direct evidence of a water phase inside single-walled carbon nanotubes that exhibits an unusual form of hydrogen-bonding due to confinement. Water adopts a stacked-ring structure inside nanotubes, forming intra- and inter-ring hydrogen bonds. The intra-ring hydrogen bonds are bulk-like while the inter-ring hydrogen bonds are relatively weak, having a distorted geometry that gives rise to a distinct OH stretching mode. The experimentally observed infrared mode at 3507 cm(-1) is assigned to vibrations of the inter-ring OH-groups based on detailed atomic-level modeling. The direct observation of unusual hydrogen bonding in nanotubes has potential implications for water in other highly confined systems, such as biological channels and nanoporous media.

Journal Article↗
PubMed2006

Mutation at Glu23 eliminates the neuron growth inhibitory activity of human metallothionein-3.

Human metallothionein-3 (hMT3), first isolated and identified as a neuronal growth inhibitory factor (GIF), is a metalloprotein expressed predominantly in brain. However, until now, the exact mechanism of the bioactivity of hMT3 is still unknown. In order to study the influence of acid-base catalysis on S-nitrosylation of hMT3, we constructed the E23K mutant of hMT3. During the course of bioassay, we found out unexpectedly that mutation at E23 of hMT3 eliminates the neuronal growth inhibitory activity completely. To the best of our knowledge, it is the first report that other residues, besides the TCPCP motif, in the beta-domain can alter the bioactivity of hMT3. In order to figure out the causes for the loss of bioactivity of the E23K mutant, the biochemical properties were characterized by UV-vis spectroscopy, CD spectroscopy, pH titration, DTNB reaction, EDTA reaction, and SNOC reaction. All data demonstrated that stability of the metal-thiolate cluster and overall structure of the E23K mutant were not altered too much. However, the reaction of the E23K mutant with SNOC exhibited biphasic kinetics and the mutant protein released zinc ions much faster than hMT3 in the initial step, while hMT3 exhibited single kinetic process. The 2D [1H-15N] HSQC was also employed to characterize structural changes during the reaction of hMT3 with varying mounts of nitric oxide. It was shown that the resonance of Glu23 disappeared at a molar ratio of NO to protein of 4. Based on these results, we suggest that mutation at Glu23 may alter the NO metabolism and/or affect zinc homeostasis in brain, thus altering the neuronal growth inhibitory activity.

Animals↗
PubMed2006

Discovery of substituted 4-anilino-2-(2-pyridyl)pyrimidines as a new series of apoptosis inducers using a cell- and caspase-based high throughput screening assay. Part 1: structure-activity relationships of the 4-anilino group.

A series of 4-anilino-2-(2-pyridyl)pyrimidines has been discovered as a new class of potent inducers of apoptosis using a cell-based HTS assay. Compound 5a was found to arrest T47D cells in G2/M and induced apoptosis. SAR studies showed that a small and electron-donating group at the meta-position of the anilino ring is important for activity. A 20-fold increase in potency, from hit compound 4-(3-methoxyanilino)-2-(2-pyridinyl)-6-(trifluoromethyl)pyrimidine (5a) to lead compound 4-(2,5-dimethoxyanilino)-2-(2-pyridinyl)-6-(trifluoromethyl)pyrimidine (5l), was obtained through the SAR studies. Compound 5l is highly active with an EC50 value of 18 nM in the caspase activation assay in T47D breast cells. Interestingly, 5a and other meta-mono-substituted compounds were active against T47D cells but were not active against H1299 and HT29 cells, while 5l and other 2,5-disubstituted compounds were active against all the three cells. In a tubulin polymerization assay, compound 5l inhibited tubulin polymerization with an IC50 value of < 0.5 microM, while 5a was not active up to 50 microM.

Aniline Compounds↗
PubMed2006

Muller glia induce retinal progenitor cells to differentiate into retinal ganglion cells.

Retinal progenitor cells could differentiate into various retinal cells that made cell-replacement therapy possible. Here, we investigated the role of cellular microenvironment on their regulation and differentiation and found that the percentage of proliferating cells and the percentage of retinal ganglion cells produced from them increased, when retinal progenitor cells were cocultured with Muller glia. Muller glia conditioned medium had the similar results. It is speculated that rather than traditional supportive roles, Muller glia may have an active regulatory role inducing retinal progenitor cells to proliferate and differentiate into ganglion cells by secreting some diffusible and membrane-associated factors. Identification of Muller glia-derived factors will be made to elucidate the molecular mechanisms of neurogenesis.

Animals↗
PubMed2006

A previously unidentified alternatively spliced isoform of t(8;21) transcript promotes leukemogenesis.

The t(8;21)(q22;q22) translocation is one of the most common genetic abnormalities in acute myeloid leukemia (AML), identified in 15% of all cases of AML, including 40-50% of FAB M2 subtype and rare cases of M0, M1 and M4 subtypes. The most commonly known AML1-ETO fusion protein (full-length AML1-ETO) from this translocation has 752 amino acids and contains the N-terminal portion of RUNX1 (also known as AML1, CBFalpha2 or PEBP2alphaB), including its DNA binding domain, and almost the entire RUNX1T1 (also known as MTG8 or ETO) protein. Although alterations of gene expression and hematopoietic cell proliferation have been reported in the presence of AML1-ETO, its expression does not lead to the development of leukemia. Here, we report the identification of a previously unknown alternatively spliced isoform of the AML1-ETO transcript, AML1-ETO9a, that includes an extra exon, exon 9a, of the ETO gene. AML1-ETO9a encodes a C-terminally truncated AML1-ETO protein of 575 amino acids. Expression of AML1-ETO9a leads to rapid development of leukemia in a mouse retroviral transduction-transplantation model. More importantly, coexpression of AML1-ETO and AML1-ETO9a results in the substantially earlier onset of AML and blocks myeloid cell differentiation at a more immature stage. These results indicate that fusion proteins from alternatively spliced isoforms of a chromosomal translocation may work together to induce cancer development.

Alternative Splicing↗
PubMed2006

Pretreatment with PTD-calbindin D 28k alleviates rat brain injury induced by ischemia and reperfusion.

Calcium toxicity remains the central focus of ischemic brain injury. Calcium channel antagonists have been reported to be neuroprotective in ischemic animal models but have failed in clinical trials. Rather than block the calcium channels, calbindin proteins can buffer excessive intracellular Ca2+, and as a result, maintain the calcium homeostasis. In the present study, we investigated the effect of calbindin D 28k (CaBD) in ischemic brain using the novel technique protein transduction domain (PTD)-mediated protein transduction. We generated PTD-CaBD in Escherichia coli, tested its biologic activity in N-methyl-D-aspartate (NMDA)- and oxygen-glucose deprivation (OGD)-induced hippocampal injury models, and examined the protection of the fusion protein using a rat brain focal ischemia model. Infarct volume was determined using 2,3,5-triphenyl-tetrazolium chloride staining; neuronal injury was examined using terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling (TUNEL) staining and cleaved caspase-3 assay. The results showed that the PTD-CaBD was efficiently delivered into Cos7 cells, hippocampal slice cells, and brain tissue. Pretreatment with PTD-CaBD decreased intracellular free calcium concentration and reduced cell death in NMDA- or OGD-exposed hippocampal slices (P<0.05). Intraperitoneal administration of PTD-CaBD before transient middle cerebral artery occlusion decreased brain infarct volume (280+/-47 versus 166+/-70 mm3, P<0.05), and improved neurologic outcomes compared with the control. Further studies showed that, compared with the control animals, PTD-CaBD decreased TUNEL (58%+/-7% versus 29%+/-3%, P<0.05)- and cleaved caspase-3 (62+/-4/field versus 31+/-6/field, P<0.05)-positive cells in the ischemic boundary zone. These results indicate that systemic administration of PTD-CaBD could attenuate ischemic brain injury, suggesting that PTD-mediated protein transduction might provide a promising and effective approach for the therapies of brain diseases, including cerebral ischemia.

Animals↗
PubMed2006

Maturation of recombinant hepatitis B virus surface antigen particles.

The major surface antigen of Hepatitis B virus (HBsAg) is a cysteine-rich, lipid-bound protein with 226 amino acids. Recombinant HBsAg (rHBsAg) with associated lipids can self-assemble into 22-nm immunogenic spherical particles, which are used in licensed Hepatitis B vaccines. Little is known about the structural evolvement or maturation upon assembly beyond an elevated level of disulfide formation. In this paper, we further characterized the maturation of HBsAg particles with respect to their degree of cross-linking, morphological changes, and changes in conformational flexibility. The lipid-containing rHBsAg particles undergo KSCN- and heat-induced maturation by formation of additional intra- and inter-molecular disulfide bonds. Direct measurements with atomic force microscopy (AFM) revealed morphological changes upon maturation through KSCN-induced and heat-/storage-incurred oxidative refolding. Particle uniformity and regularity was greatly improved, and protrusions formed by the protein subunits were more prominent on the surface of the mature particles. Decreased conformational flexibility in the mature rHBsAg particles was demonstrated by millisecond-scale unfolding kinetics in the presence of an environment-sensitive conformation probe. Both the accessible hydrophobic cavities under native conditions and the changeable hydrophobic cavities upon denaturant-induced unfolding showed substantial decrease upon maturation of the rHBsAg particles. These changes in the structural properties may be critical for the antigenicity and immuno-genicity of this widely-used vaccine component.

Disulfides↗
PubMed2006

Evaluation of the thermal stability of Gardasil.

The thermostability of GARDASIL (Merck & Co., Inc, Whitehouse Station, NJ, USA), a developmental vaccine against human papillomavirus (HPV), was evaluated using an enzyme immunoassay, referred to as the in vitro relative potency (IVRP) assay and differential scanning calorimetry (DSC). Gardasil samples were stored at temperatures ranging from 4 to 42 degrees C and tested for IVRP at various time points. Extrapolation of the IVRP results indicates GARDASIL is extremely stable. The half-life of the vaccine is estimated to be 130 months or longer at temperatures up to 25 degrees C. At 37 degrees C, the half-life is predicted to be 18 months and at 42 degrees C, the half-life is predicted to be approximately three months. Differential scanning calorimetry (DSC) analysis was used to evaluate the process of protein denaturation during a rapid temperature increase (as opposed to long-term storage at a specific temperature). Differences were seen among the DSC profiles of the four HPV types tested. This indicates that small differences in the amino acid structure can have a significant effect on the intermolecular contacts that stabilize the L1 proteins and the VLP assembly. For the Gardasil samples evaluated here, DSC results demonstrated the relative overall structural stability of the VLPs, but were not predictive of the excellent long-term stability observed with the IVRP assay.

Calorimetry, Differential Scanning↗
PubMed2006

In vitro and in vivo intracellular liposomal delivery of antisense oligonucleotides and anticancer drug.

The specific aims of this investigation were (1) to show that conventional and PEGylated liposomes can penetrate cancer cells in vitro and in vivo; (2) to demonstrate that liposomes can be successfully used both for cytoplasmic and nuclear delivery of therapeutics, including anticancer drugs and antisense oligonucleotides; (3) to examine the specific activity of anticancer drugs and nucleotides delivered inside tumor cells by PEGylated liposomes; and (4) to confirm that simultaneous inhibition of pump and nonpump cellular resistance by liposomal ASO can substantially enhance the antitumor activity of traditional well established anticancer drugs in mice bearing xenografts of human multidrug resistant ovarian carcinoma. Experimental results show that PEGylated liposomes are capable of penetrating directly into tumor cells after systemic administration in vivo and do successfully provide cytoplasmic and nuclear delivery of encapsulated anticancer drug (doxorubicin, DOX) and antisense oligonucleotides (ASO). Encapsulation of DOX and ASO into liposomes substantially increased their specific activity. Simultaneous suppression of pump and nonpump resistance dramatically enhanced the ability of DOX for inducing apoptosis leading to higher in vitro cytotoxicity and in vivo antitumor activity.

Animals↗
PubMed2006

Gadd45a interacts with aurora-A and inhibits its kinase activity.

Centrosome stability is required for successful mitosis in mammalian cells. Amplification of the centrosome leads to chromosomal missegregation and generation of aneuploidy, which are closely associated with cell transformation and tumorigenesis (Doxsey, S. J. (2001) Nat. Cell Biol. 3, E105-E108; Hinchcliffe, E. H., and Sluder, G. (2001) Genes Dev. 15, 1167-1181; Pihan, G. A., Purohit, A., Wallace, J., Malhotra, R., Liotta, L., and Doxsey, S. J. (2001) Cancer Res. 61, 2212-2219). However, there are currently limited insights into mechanism(s) for this critical biological event. Here we show that Gadd45a, a DNA damage-inducible protein that is regulated by tumor suppressors p53 and BRCA1, participates in the maintenance of centrosome stability. Mouse embryonic fibroblasts derived from gadd45a knock-out mice exhibit centrosome amplification (designated as increased centrosome numbers). Introduction of exogenous Gadd45a into mouse embryonic fibroblasts isolated from gadd45a-null mice substantially restored the normal centrosome profile. In contrast to p21(waf1/cip1), which ensures coordinated initiation of centrosome, Gadd45a had no significant effect on centrosome duplication in S phase. Interestingly Gadd45a was found to physically associate with Aurora-A protein kinase, whose deregulated expression results in centrosome abnormality. Furthermore Gadd45a was demonstrated to strongly inhibit Aurora-A kinase activity and to antagonize Aurora-A-induced centrosome amplification. These findings identify a novel mechanism for Gadd45a in the maintenance of centrosome stability and broaden understandings of p53- and BRCA1-regulated signaling pathways in maintaining genomic fidelity.

Animals↗
PubMed2006

Hypoxia differentially regulates the expression of neuroglobin and cytoglobin in rat brain.

Neuroglobin (Ngb) and Cytoglobin (Cygb) are new members of the globin family and display heterotopic expression patterns. To examine the effect of different hypoxia profiles on expression of Ngb and Cygb in rodent brain, rats were exposed to either sustained hypoxia (SH; 10% O(2)) or intermittent hypoxia (IH; 10% and 21% O(2) alternating every 90 s) for 1, 3, 7 and 14 days, and mRNA and protein expression of Ngb and Cygb were assessed in brain cortex. SH increased Ngb mRNA and protein expression throughout the exposure, while IH only elicited slight increases in Ngb expression at day 1. Neither SH nor IH elicited increases in Cygb expression. Thus, hypoxic stimulus presentation is a major determinant of the regulation of hypoxic sensitive genes such as Ngb. Furthermore, disparities between Ngb and Cygb responses to hypoxia further suggest that these two globins may play divergent roles in brain.

Animals↗
PubMed2006

[Isolation, purification and immunochemical characteristics of spermatogonia of rat].

OBJECTIVE: To explore the approach of isolation and purification of spermatogonia and its immunochemical characteristics. METHODS: Compound enzymatic digestions were used to prepare germ cell suspensions of Sprague-Dawley rats aged 10 days, and velocity sedimentation and discontinuous Percoll density gradient centrifugation were used to isolate and purify the spermatogonia. Using c-kit and alpha(6)-integrin multiclone antibodies as markers respectively, the immunochemical characteristics of the spermatogonia in the testicular tissue were observed and the c-kit and alpha(6)-integrin expression rates of the purified cells were detected by flow cytometry. RESULTS: The spermatogonia uniquely expressed c-kit and alpha(6)-Integrin in the testicular tissue. C-kit and alpha(6)-integrin were positively expressed in the purified cell suspensions. Using c-kit as the cell marker, the positive rate was 1.59% +/- 0.04% in the unpurified group, significantly lower than that of the purified group (68.33% +/- 2.45%, P < 0.01). Using alpha(6)-integrin as the cell marker, the positive rate of the unpurified group was 2.38% +/- 0.60%, significantly lower than that of the purified group (72.04% +/- 3.65%, P < 0.01). Trypan blue staining showed that the cell viability of the purified cell suspensions was more than 95%. CONCLUSION: c-kit and alpha(6)-integrin can be used as the molecular markers of spermatogonium at special stage. Spermatogonia with high purity and viability can be obtained via the steps including digestions with enzymes, velocity sedimentation and discontinuous percoll density gradient centrifugation.

Animals↗
PubMed2006

Individual solar-UV doses of pupils and undergraduates in China.

The solar-UV exposures of school pupils and medical undergraduates were studied over four seasons in Shenyang (latitude 41 degrees 11'-43 degrees 2', longitude 122 degrees 25'-123 degrees 48'), Liaoning, PR China. Ultraviolet exposure was measured using personal ultraviolet radiation (UVR) sensor on sunny days along with simultaneous monitoring and recording of direct-ambient UVR dose (perpendicular UV dose) for comparison. We observed that the UV doses of pupils on weekdays were higher than those on weekends and that the UV doses of the pupils were significantly higher than those of the undergraduates during both weekdays and weekends. The percent of the mean individual daily UV dose to the environmental counterpart are 2.88% (Autumn), 7.76% (Winter), 3.77% (Spring) and 2.06% (Summer) for the pupils, and corresponding percent for the undergraduates are 0.88%, 0.32%, 0.67% and 0.81%. The means of minimum erythemal dose values with pupils for weekday (5 days), weekend (2 days) and week (7 days) through the whole year are 0.302 (0.275 ~ 0.328), 0.215 (0.170 ~ 0.261) and 0.278 (0.255 ~ 0.301), respectively. The corresponding means with undergraduates are 0.097 (0.081~ 0.113), 0.091 (0.070 ~ 0.112) and 0.095 (0.082 ~ 0.108), respectively. Although the season is a major factor influencing the personal direct-ambient percent, it is emphasized that the impact of the lifestyle cannot be ignored.

Adult↗