Biomedical subjects

Y Cai

Publications and source records attributed to Y Cai.

At least 19 recordsLinked to original sources

PubMed2006

Fermentation quality and nutritive value of a total mixed ration silage containing coffee grounds at ten or twenty percent of dry matter.

Six wethers were used in a replicated 3 x 3 Latin square to study the fermentation quality and nutritive value of total mixed ration (TMR) silages that included wet coffee grounds (WCG). The TMR were prepared using a commercial compound feed, timothy hay, alfalfa hay, dried beet pulp, and a vitamin-mineral supplement in a ratio of 36.5:30:20:12:1.5, respectively, on a DM basis, with timothy hay and alfalfa hay being replaced by WCG at 0, 10, or 20%. All TMR silages, irrespective of WCG addition, were well preserved, with a low pH and ammonia-N content and a high lactic acid content. Intakes by wethers of TMR silages containing 0 and 10% WCG were 96.6 and 94.8 g/kg of BW(0.75), and did not differ (P > 0.05). Intake of TMR silage containing 20% WCG was 76.8 g/kg of BW(0.75), which was equal to 80% of that of the TMR silage with no WCG (quadratic: P < 0.01). Increasing concentrations of WCG in the rations decreased the digestibility of DM, CP, ADF, NDF, and energy, and increased that of ether extract (P < 0.05). The TDN and DE contents of the TMR silages with 0 and 10% WCG were similar, but the TMR silage with 20% WCG was lower (P < 0.05). With progressive increases in WCG concentrations, N intake did not differ, but fecal and urinary N increased linearly (P < 0.001), and retained N decreased linearly (P < 0.001). This study demonstrated that the proportion of WCG to be incorporated into TMR silages should not exceed 10% of the DM.

Ammonia↗

PubMed2006

NO adsorption and dissociation on Rh(111): PM-IRAS study.

We have used in situ polarization-modulation infrared reflection absorption spectroscopy to study the adsorption/dissociation of NO on Rh(111). While these studies have not been conclusive regarding the detailed surface structures formed during adsorption, they have provided important new information on the dissociation of NO on Rh(111). At moderate pressures (< or =10(-6) Torr) and temperatures (<275 K), a transition from 3-fold hollow to atop bonding is apparent. Data indicate that this transition is not due to the migration of the 3-fold hollow NO but rather to the adsorption of gas-phase NO that is directed toward the atop position due to the presence of NO decomposition products, particularly chemisorbed atomic O species at the hollow sites. These results indicate that NO dissociation occurs at temperatures well below the temperature previously reported. Additionally, high pressure (1 Torr) NO exposure at 300 K results in only atop NO, calling into question the surface structures previously proposed at these adsorption conditions consisting of atop and 3-fold hollow sites.

Journal Article↗

PubMed2006

A novel carbon nanotube structure formed in ultra-long nanochannels of anodic aluminum oxide templates.

We report the fabrication of a novel carbon structure consisting of uniform carbon nanotubes formed in the nanochannels of anodic aluminum oxide (AAO) templates, with the surface side open and connected by a uniform carbon sheet. The uniformity of the fabricated CNT arrays, plus the carbon film on the AAO surface interconnecting the open ends of all CNTs, constitute the major characteristics unique to our carbon structures. Some potential applications of such structures are noted.

Journal Article↗

PubMed2006

Gene expression profiling and analysis of signaling pathways involved in priming and differentiation of human neural stem cells.

Human neural stem cells have the ability to differentiate into all three major cell types in the CNS including neurons, astrocytes and oligodendrocytes. The multipotency of human neural stem cells shed a light on the possibility of using stem cells as a therapeutic tool for various neurological disorders including neurodegenerative diseases and neurotrauma that involve a loss of functional neurons. We have discovered previously a priming procedure to direct primarily cultured human neural stem cells to differentiate into almost pure neurons when grafted into adult CNS. However, the molecular mechanism underlying this phenomenon is still unknown. To unravel transcriptional changes of human neural stem cells upon priming, cDNA microarray was used to study temporal changes in human neural stem cell gene expression profile during priming and differentiation. As a result, transcriptional levels of 520 annotated genes were detected changed in at least at two time points during the priming process. In addition, transcription levels of more than 3000 hypothetical protein encoding genes and EST genes were modulated during the priming and differentiation processes of human neural stem cells. We further analyzed the named genes and grouped them into 14 functional categories. Of particular interest, key cell signal transduction pathways, including the G-protein-mediated signaling pathways (heterotrimeric and small monomeric GTPase pathways), the Wnt signaling pathway and the TGF-beta pathway, are modulated by the neural stem cell priming, suggesting important roles of these key signaling pathways in priming and differentiation of human neural stem cells.

Bone Morphogenetic Proteins↗

PubMed2005

Nutrient sensing in pancreatic beta cells suppresses mitochondrial superoxide generation and its contribution to apoptosis.

Excessively high glucose concentrations have been shown to damage tissues through stimulation of mitochondrial superoxide generation. This effect has therefore been considered as a potential cause for dysfunction and death of pancreatic beta cells in diabetes. We have examined whether the rate of glucose metabolism in isolated rat beta cells is correlated with their formation of oxygen radicals. It was found that high rates of glucose metabolism did not stimulate the formation of superoxide and H(2)O(2) but suppressed it. The higher rates of superoxide production in beta cells with lower mitochondrial metabolic activity contributed to the susceptibility of these cells to apoptosis.

Animals↗

PubMed2005

Clinical study of recombinant adenovirus-p53 (Adp53) combined with hyperthermia in advanced cancer (a report of 15 cases).

The study was to evaluate the efficacy of the Adp53 combined with hyperthermia on advanced cancer. Fifteen patients with advanced cancer were enrolled in this clinical trial. Thirteen patients with recurrent tumours failed in conventional treatments and the two other patients with primary tumour received no treatment before they were enrolled. Recombinant adenovirus-p53 (Adp53) is a E1 substituted replication-incompetent recombinant adenovirus encoding the human wild-type p53 (wtp53) gene. The 15 patients were intra-tumourally injected with Adp53, 1x10(12)vp (virus particle) once a week, with a total of 4-8 times was given. The temperature being set hyperthermia every week 3 days after the injection of Adp53 at 43-44 degrees C using 915 MHz microwave machine for superficial tumour for 1 h or at 42-43 degrees C using 41 MHz radiofrequency machine for deep-seated tumour for 1 h. Among the 15 patients, five concurrently were added with radiotherapy and three were added with cisplatin-based chemotherapy. The treatment achieved CR in two cases, PR in four cases, SD in eight cases and PD in one case and, after the treatment, tumours of two cases disappeared and seven of the other 13 cases (54%) had low-density area (LDA) of more than 50% on CT images in tumours. In the 15 patients, no dose-limiting toxicity and adverse events were noted, except transient fever after Adp53 administration. In conclusion, Adp53 combined with hyperthermia was safe and effective in patients with advanced cancer and p53 gene therapy was potential to thermosensitize in advanced cancer.

Adenoviruses, Human↗

PubMed2005

A combination of anergic cells' adoptive transfer and rapamycin therapy prolongs cardiac allograft survival in mice.

The in vivo immunoregulatory effect of anergic cells induced by blocking the costimulatory pathway was investigated in this study. Anergic cells were generated in vitro by mixed culture of murine splenic cells from BALB/c and C3H/HeJ under the blockade of anti-CD154 and anti-CD80 monoclonal antibodies, and the in vitro activity of anergic cells were observed. The 3.0 Gy gamma-irradiated BALB/c mice received cardic allografts from C3H/HeJ, and anergic cells were intravenously injected immediately after transplantation. Recipient mice injected with anergic cells also received rapamycin therapy (1 mg/kg/day) for 14 days. On day 7 after transplantation, the subsets of peripheral blood T lymphocytes, the pathology of grafts and the infiltration of lymphocytes in grafts were analysed. Untreated gamma-irradiated animals showed a graft median survival time (MST) of 9 days. Animals injected with anergic cells only or receiving rapamycin therapy alone showed MST of 11 and 17 days, respectively. MST of allograft in mice treated with control cells plus rapamycin therapy was 9 days. Animals injected with anergic cells plus rapamycin therapy, but receiving third-party allografts (C57BL/6J), showed an MST of 15 days. However, anergic cell injection plus rapamycin therapy prolonged allograft survival significantly (MST 28 days, P < 0.01). The rejection was mild and tissue architecture was preserved in recipient mice receiving anergic cell injection plus rapamycin therapy. Furthermore, anergic cells and rapamycin therapy decreased the percentage of peripheral blood CD4+ and CD8+ T cells (including CD25+, CD152+, CD154+ and CD28+ subsets) and greatly reduced the infiltrating lymphocytes in allografts (including CD3+, CD4+, CD8+ and CD25+ T cells). In conclusion, the treatment based on anergic cells' adoptive transfer plus rapamycin therapy demonstrated a significant prolongation of murine cardiac allograft survival in a donor antigen-specific manner. This therapeutic protocol alleviated allograft rejection to solid allograft in vivo.

Adoptive Transfer↗

PubMed2005

New criteria for immunofluorescence assay for Q fever diagnosis in Japan.

A study was made to evaluate the cutoff value of indirect immunofluorescent-antibody (IFA) test for Q fever diagnosis in Japan. We used 346 sera, including 16 from confirmed Q fever cases, 304 from Japanese pneumonia patients, and 26 from negative cases. Thirteen sera from the confirmed Q fever cases with an immunoglobulin M (IgM) titer of > or =1:128 and/or IgG titer of > or =1:256 by the IFA test were positive by both enzyme-linked immunosorbent assay (ELISA) and Western blotting assay (WBA), whereas 298 sera from pneumonia patients and 26 negative sera with an IgM titer of < or =1:16 and an IgG titer of < or =1:32 by the IFA test were negative by both ELISA and WBA. In the proposed "equivocal area," with an IgM titer of > or =1:32 and < or =1:64 and/or an IgG titer of > or =1:64 and < or =1:128, we found 9 sera, 3 from confirmed Q fever cases and 6 from Japanese pneumonia patients, by the IFA test. Three sera from the confirmed Q fever cases and one of the sera from pneumonia patients were IgM and/or IgG positive by both ELISA and WBA. These results suggest that a single cutoff value for the IFA test may cause false-positive and false-negative results. In conclusion, this study showed that an "equivocal area" should be used for the IFA test rather than a single cutoff value and that sera in the equivocal area should be tested by additional serological assays for confirmation.

Antibodies, Bacterial↗

PubMed2004

Steady-state fluorescence study on release of camptothecin from agar hydrogel.

The slow drug release processes from agar hydrogel were studied by steady-state fluorescence (SSF) measurement. An anticancer drug, camptothecin (CPT), was used as the release drug and the fluorescence probe for the real-time monitoring of the release processes by measuring the fluorescence intensity of the probe. The release kinetics of CPT at different temperatures was investigated. The Fickian diffusion model was adopted to fit the results and a good linear relationship could be observed between the logarithmic release fraction and the releasing time. The diffusion coefficients (D) at these conditions were thus obtained from the slopes of the fitting curves. By plotting D against temperature, the diffusion coefficient of CPT was found to obey the Arrhenius relation and the activation energy was then obtained to be 70.6 kJ mol(-1).

Agar↗

PubMed2004

Beam-beam limit in e+e- circular colliders.

Beam-beam effects limit the luminosity of circular colliders. Once the bunch population exceeds a threshold, the luminosity increases at a slower rate. This phenomenon is called the beam-beam limit. Onset of the beam-beam limit has been analyzed with various simulation methods based on the weak-strong and strong-strong models. We have observed that an incoherent phenomenon is mainly concerned in the beam-beam limit. The simulation have shown that equilibrium distributions of the two colliding beams are distorted from Gaussians when the luminosity is limited. The beam-beam limit is estimated to be xi approximately 0.1 for a B factory with damping time of several thousand turns.

Journal Article↗

PubMed2004

Effect of Endo-GIA vascular staple size on laparoscopic vessel sealing in a porcine model.

BACKGROUND: Two sizes of endoscopic gastrointestinal anastomosis (Endo-GIA) staples are currently available for vascular control. The purpose of this study was to compare the Endo-GIA 30-2.0 mm with the Endo-GIA 30-2.5 mm vascular staple. METHODS: The renal blood vessels, aorta, and vena cava were divided laparoscopically using the Endo-GIA 30-2.0 and 30-2.5 mm in four pigs, respectively. The arterial and venous segments were harvested en bloc for ex vivo burst pressure studies. RESULTS: Both 2.0-mm and 2.5-mm staples achieved vessel sealing at supraphysiologic mean burst pressures (> or =310 mmHg). There were no statistical differences between mean burst pressures of vessels stapled by 2.0-mm compared to 2.5-mm staples. Both staples sealed arteries up to 17 mm and veins up to 22 mm in diameter. CONCLUSION: Endo-GIA 30-2.0 mm and 30-2.5 mm vascular staples are equivalent in sealing vessels at supraphysiologic mean burst pressures.

Anastomosis, Surgical↗

PubMed2004

Are new-generation flexible ureteroscopes better than their predecessors?

OBJECTIVE: To compare two newly designed flexible ureteroscopes with their respective predecessors, to determine whether design advances have overcome the limitation of tip deflection, which may interfere with diagnosis and treatment of lower pole renal pathology. MATERIALS AND METHODS: Two new-generation flexible ureteroscopes, the DUR-8 Elite (ACMI, Southborough, MA, USA) and 11278AU (Karl Storz Endoscopy, Culver City, CA, USA) were compared with their previous models, the ACMI DUR-8 and the Storz 11274AAU. Active tip deflection and irrigation flow rates with and without various endoscopic tools were assessed. Specifications, purchase prices and repair costs were obtained from each manufacturer. The field of view and screen image size of each ureteroscope were also compared. RESULTS: The ACMI DUR-8 Elite and the Storz 11278AU had improvements of 79 degrees and 144 degrees, respectively, from their respective older models. Although the tip deflection of all ureteroscopes was compromised by inserting different endoscopic tools, these new instruments were less affected. With a 3 F basket inside the working channel, the ACMI DUR-8 Elite and the Storz 11278AU had only 0.7% and 2.8% loss of upward tip deflection, compared with their older models, at 9.6% and 5.0%, respectively. However, the flow rates of these new instruments were decreased. CONCLUSION: The new flexible ureteroscopes have significantly better active tip deflection than previous models, both with and without endoscopic instrumentation inserted. However, improved flexibility is at the expense of decreased flow rates and higher purchase costs.

Equipment Design↗

PubMed2003

RPGRIP1s with distinct neuronal localization and biochemical properties associate selectively with RanBP2 in amacrine neurons.

RPGR and RPGRIP1 are molecular partners with vital roles in retinal function. Mutations in RPGR are implicated in heterogeneous retinal phenotypes, while those in RPGRIP1 lead to Leber congenital amaurosis. RPGR and RPGRIP1s differentially localize in photoreceptors among species. This may contribute to phenotype disparities among species bearing mutations in RPGR. However, it cannot account for the phenotype heterogeneity associated with RPGR- and RPGRIP1-linked mutations in the human. The existence of RPGRIP1 isoforms with distinct cellular, subcellular localizations and biochemical properties in the retina is shown. High mass RPGRIP1 isoforms, p175/p150, enriched in the outer segment (OS) compartment of photoreceptors are identified. The remaining isoforms are present across subcellular fractions, including nuclei and are soluble. The p175/p150 are predominantly sequestered in the cytoskeleton-insoluble fraction of OS and nuclei. In selective amacrine cells, and in the transformed photoreceptor line, 661W, RPGRIP1s localize at restricted foci to nuclear pore complexes and/or the vicinity of these. Among the nucleoporins, RPGRIP1 isoforms selectively associate in vivo with RanBP2 (Nup358). RPGRIP1s also decorate microtubules in 661W cells and occasionally form coiled-like inclusion bodies in the perikarya. These results support distinct but complementary functions of RPGRIP1 isoforms in cytoskeletal-mediated processes in photoreceptors and amacrine neurons, and may explain the Leber phenotype linked to RPGRIP1 mutations in humans. Moreover, the data implicate a role of RanBP2 in the pathogenesis of neuro(retino)pathies and as a docking station to mediate the nucleocytoplasmic shuttling of RPGRIP1s and their interaction with other partners in amacrine and 661W neurons.

Amacrine Cells↗

PubMed2003

Ion trap mass spectrometry of fluorescently labeled nanoparticles.

Mass spectra of fluorescently labeled polystyrene nanoparticles have been obtained using a combined technique of matrix-assisted laser desorption/ionization (MALDI), laser-induced fluorescence (LIF), and a dual quadrupole ion trap mass spectrometer. The spectrometer is designed in such a way that the first trap serves as a trapping and mass-analyzing device, while the second trap serves to capture and concentrate the ions ejected from the first trap for fluorescence detection. An enhancement in the LIF signal by more than 3 orders of magnitude is achieved with the help of the second trap, making mass/charge (m/z) analysis of the nanoparticles possible. Additional unique features of this mass spectrometer include that frequency scan (0.5-50 kHz) at a constant voltage (200 V), instead of voltage scan at a constant frequency, is implemented to widen the spectral analysis range of the instrument. The implementation has allowed the spectrometer to operate at relatively high buffer gas pressures (50 mTorr), crucial for effective trapping of the nanometer-sized particles generated by MALDI. We present in this report the first mass spectra of fluorescently labeled nanoparticles with a size of 27 nm using this new mass spectrometric approach. The utility of this method in the study of biological macromolecules or particles is demonstrated with dye-labeled IgG.

Journal Article↗

PubMed2003

Astilbin suppresses collagen-induced arthritis via the dysfunction of lymphocytes.

OBJECTIVE AND DESIGN: To examine the therapeutic effects of astilbin, a flavanoid isolated from Rhizoma Smilacis Glabrae, on arthritis and to compare it with cyclosporine A (CsA). MATERIALS AND METHODS: Type II collagen-induced arthritis in mice and its in vitro assays for proliferation, matrix metalloproteinase (MMP) and NO production were performed. RESULTS: Astilbin dose-dependently inhibited the footpad swelling, arthritic incidence, and clinical scores without influencing the body weights, while CsA showed strong inhibition with a significant weight loss. Histological examination revealed marked inflammatory damage in arthritic mice including joint swelling, synovial hyperplasia, and cartilage destruction. Against these, an intact joint structure was maintained in astilbin-treated or CsA-treated mice. In isolated spleen cells from arthritic mice, increased potentials in proliferation, NO production, and MMP-2 and 9 activities were suppressed dose-dependently by the oral administration of astilbin. Additionally, astilbin showed neither any cytotoxicity to nor influence on Con A-induced proliferation of spleen cells from naive mice, while CsA showed a dose-dependent cytotoxicity and inhibition of the proliferation. CONCLUSIONS: Astilbin may act as an efficient therapeutic agent for arthritis like CsA but with less toxicity. Its mechanism includes a selective suppression on lymphocyte functions via reducing MMP and NO production.

Animals↗

PubMed2003

Examination stress in Singapore primary schoolchildren: how compliance by subjects can impact on study results.

OBJECTIVE: Examinations are anecdotally viewed as extremely stressful to Singapore schoolchildren. We test this postulate by obtaining parental ratings of children's emotional stress levels longitudinally in a large representative sample of sixth (P6) and fifth (P5) class primary schoolchildren, respectively, exposed and unexposed to a streaming examination. METHOD: Children's stress levels were rated monthly by a parent for 10 months. RESULTS: Analyses failed to find evidence of any differential stress impact across P6 and P5 comparison groups, apart from a subset of P6 children whose parents complied with every monthly survey. CONCLUSION: The streaming examination in the final year of primary school did not emerge as a general stressor to children, but achieved salience within a defined subset of children whose parents were highly study compliant. Study compliance may be a proxy variable of some import, and have wider relevance to other cohort studies and to intervention trials.

Child↗

PubMed2003

AMP-activated protein kinase can induce apoptosis of insulin-producing MIN6 cells through stimulation of c-Jun-N-terminal kinase.

We have recently shown that conditions known to activate AMP-activated protein kinase (AMPK) in primary beta-cells can trigger their apoptosis. The present study demonstrates that this is also the case in the MIN6 beta-cell line, which was used to investigate the underlying mechanism. Sustained activation of AMPK was induced by culture with the adenosine analogue AICA-riboside or at low glucose concentrations. Both conditions induced a sequential activation of AMPK, c-Jun-N-terminal kinase (JNK) and caspase-3. The effects of AMPK on JNK activation and apoptosis were demonstrated by adenoviral expression of constitutively active AMPK, a condition which reproduced the earlier-described AMPK-dependent effects on pyruvate kinase and acetyl-coA-carboxylase. The effects of JNK activation on apoptosis were demonstrated by the observations that (i). its inhibition by dicumarol prevented caspase-3 activation and apoptosis, (ii). adenoviral expression of the JNK-interacting scaffold protein JIP-1/IB-1 increased AICA-riboside-induced JNK activation and apoptosis. In primary beta-cells, AMPK activation was also found to activate JNK, involving primarily the JNK 2 (p54) isoform. It is concluded that prolonged stimulation of AMPK can induce apoptosis of insulin-producing cells through an activation pathway that involves JNK, and subsequently, caspase-3.

AMP-Activated Protein Kinases↗

PubMed2002

Optical detection and charge-state analysis of MALDI-generated particles with molecular masses larger than 5 MDa.

Charged polystyrene nanoparticles are generated by matrix-assisted laser desorption/ionization (MALDI) and detected by laser-induced fluorescence (LIF) in a quadrupole ion trap. Employing the LIF technique, observations of individual fluorescent nanospheres (27 nm in diameter and containing 180 fluorescein dye equivalents) have been achieved with an average signal-to-noise ratio of approximately 10. With the trap operating at a frequency around 5 kHz, charge state analysis of the particles reveals that the number of charges carried by the spheres is between 1 and 10. It suggests a mass-to-charge ratio (m/z) in the range of 10(5)-10(6) for the MALDI-generated particles. To effectively trap such large particles (m > 5 MDa), damping of the particles' motions by using approximately 50 mTorr He buffer gas is absolutely required. Similar findings are obtained for particles with a nominal size of 1 microm in diameter, demonstrating that production of charged particles with a molecular mass as high as 10(12) Da is possible using the MALDI technique.

Fluorescent Dyes↗