Biomedical subjects

D Yuan

Publications and source records attributed to D Yuan.

At least 19 recordsLinked to original sources

PubMed2004

Metal ion reduction and resultant deposition on viologen-functionalized LDPE films and viologen-containing microporous membranes.

Photo-induced reduction of gold and platinum metal salt solutions was carried out using viologen graft copolymerized on low-density polyethylene (LDPE) films and viologen-containing poly(vinylidene fluoride) (PVDF-PVBV) microporous membranes. The effects of the UV irradiation time and concentration of the metal salt solutions on the metal ion reduction process and the resultant metal deposition on the polymeric substrates were investigated. The metal-polymer composites were characterized using X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy (SEM and TEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and UV-visible absorption spectroscopy. The amount of metal uptake, the state of the metal, and the size of the metal particles were found to be strongly dependent on the UV irradiation time and the type and concentration of the metal salt solution. The microporous structure and the high viologen content of the PVDF-PVBV membrane constitute an effective matrix for metal ion reduction and preparation of metal nanoparticles.

Gold↗

PubMed2001

IFN-gamma-dependent and -independent initiation of switch recombination by NK cells.

We have examined the effect of IL-2-propagated NK or NK-T cells on each of the steps required for B cell switch recombination leading to IgG2a production. The results indicate that NK cells, on their own and in the absence of IFN-gamma, can induce germline transcription in resting, IgG(-) B lymphocytes from the gamma2a locus as well as mRNA for activation-induced cytidine deaminase (AID) via a process that requires cell-cell interactions. The results also show that, in contrast to induction by T cells, activation by NK cells does not involve CD40-CD40 ligand interactions and does not extend to the induction of Igamma1 transcription. Furthermore, in contrast to stimulation by LPS and IFN-gamma or by T cells, the activation events initiated by NK cells do not result in significant synthesis of functional gamma2a mRNA in resting B lymphocytes even in the presence of IFN-gamma. Thus, induction of germline and AID transcripts are necessary but not sufficient events for functional switching to IgG2a. These experiments, showing that NK cells themselves cannot induce IgG2a production but can polyclonally program B lymphocytes so that they preferentially switch to this isotype may explain how activated NK cells can skew the Ag-specific immune response toward IgG2a. The findings also provide further demonstration of the definitive yet limited extent of how a non-Ag-specific component of the innate system can modulate the direction of the adaptive immune response.

Animals↗

PubMed2001

Inappropriate expression of IgD from a transgene inhibits the function of antigen-specific memory B cells.

IgD expression has been shown to be downmodulated upon mitogenic or antigenic activation of B cells. To investigate whether this decrease is of functional significance we studied a mouse strain that expresses transgenic IgD on all B cells. The rearranged gene encoding the heavy chain of this IgD requires endogenous gene rearrangement before it can be expressed; therefore, normal B cell development is not affected. As a result, both transgenic IgD and endogenous IgM and IgD are expressed on all peripheral B cells. We show that the presence of extraneous IgD does not affect normal B cell activation by polyclonal stimulators, nor does it affect the primary IgM or IgG responses to TI or TD antigens. However, the secondary memory response is significantly diminished. The decrease is not attributable to a defective generation of memory B cells; instead the activation of memory cells appears to be compromised. Since the depressed response can be overcome by prior aggregation of the transgenic IgD with allotype-specific anti-IgD antibodies, it appears that persistence of the transgenic IgD on memory cells may influence their ability to be activated. Thus, the decrease in IgD expression on normal B cells after activation may be necessary for optimal activation of memory cells.

Animals↗

PubMed2001

Uptake and distribution of rare earth elements in rice seeds cultured in fertilizer solution of rare earth elements.

The uptake behavior of rare earth elements (REEs) under pot conditions using deionized water and a REE fertilizer solution as the culture media as well as the distribution of REEs in rice proteins were studied. The uptake of REEs in rice seeds increased dramatically after a lag period of approximately three days. Roots can accumulate a much higher content of REEs than germs and the resting seeds. The REE content in each water-soluble (albumin) and salt-soluble (globulin) component of the rice seeds accounted for 5-8% and 4-6% of the total REEs, respectively. However, there are less than 1.5% of the total REEs were found in the alcohol-soluble (prolamin) and acetic acid-soluble (glutelin) components. The high performance liquid chromatography (HPLC) in the gel permeation and the reserved-phase were used to monitor changes in the molecular weight distribution changes of the soluble proteins of rice seeds during germination after having been cultured in the same solution for seven days. No changes occurred in the prolamin, while a slight change occurred in the albumin, globulin and glutelin. Fractionation of the albumin of rice seeds cultured in a REE fertilizer solution on the Sephadex G-100 column indicated that REEs, especially Ce, La, Pr and Nd, were associated mainly with biological compounds of a molecular weight between 10,000 and 12,000.

Absorption↗

PubMed2001

Status of persistent organic pollutants in the sediment from several estuaries in China.

Sediment samples from three estuaries on the east coast of China were analyzed for persistent organic pollutants. Total PCB, PAH, and DDT concentrations in the sediments from Minjiang, Jiulongjiang, and Zhujiang estuaries ranged from 2 to 14 ng/g, 400 to 1500 ng/g, and 6 to 73 ng/g, respectively, in the sediments from these estuaries. The sources of PAH contamination were inferred from PAH compositions, with pyrogenic PAHs being the dominant source for Minjiang Estuary and petroleum related PAHs being the primary contributors to Jiulongjiang and Zhujiang estuaries. The high concentrations of DDT in the sediments from these estuaries were likely the result of widespread use of DDT in China in the 1960s and 1970s. Butyltin compounds were detected in the sediment from Jiulongjiang Estuary and Victoria Harbor, Hong Kong. Presence of butyltin compounds probably result from the shipping activities in these estuaries. Butyltin compounds were not detected in the sediments from Minjiang and Zhujiang estuaries. Contaminant concentrations were generally below levels expected to affect benthic organisms with the exception of DDTs.

Animals↗

PubMed2001

Pulsed tissue Doppler imaging to assess myocardial viability by quantification of regional myocardial functional reserve.

Dobutamine stress echocardiography (DSE) is used widely to evaluate myocardial viability, but is limited by the subjective nature of test interpretation. Assessment of systolic function by pulsed tissue Doppler imaging (TDI) during dobutamine stimulation may allow a more objective evaluation of myocardial functional reserve and, thus, myocardial viability. In 30 patients (58 +/- 9 years) with prior myocardial infarction, pulsed TDI with low dose dobutamine stress (10 microg/kg/min) was performed to assess myocardial viability. Qualitative assessment of two-dimensional (2-D) DSE and positron emission tomography (PET) were used for comparison. Peak systolic myocardial velocity was measured for each left ventricular segment (16 segments) at baseline and low dose dobutamine stress using pulsed TDI. The absolute and relative increases of peak systolic velocity from rest to low dose dobutamine stress were calculated. Three hundred sixty-four segments with adequate pulsed TDI tracing were divided according to either 2-D DSE or PET findings into normal, viable (mismatch), and nonviable (match) segments. The increase of peak systolic myocardial velocity from baseline to low dose dobutamine was significantly different between segments defined as normal, viable, and nonviable by 2-D DSE (2.71 +/- 1.91 cm/sec, 1.86 +/- 2.15 cm/sec, and 0.99 +/- 1.16 cm/sec, respectively; P < 0.001). The increase of peak systolic myocardial velocity from rest to low dose dobutamine for normal, mismatch, and match segments defined by PET was 2.72 +/- 1.96, 1.01 +/- 0.96 and 0.80 +/- 1.07 cm/sec, respectively (P < 0.001). In conclusion, the increase of peak systolic myocardial velocity during low dose dobutamine stimulation determined by pulsed TDI distinguishes between different myocardial viability states. It complements the standard interpretation of stress echocardiograms.

Aged↗

PubMed2001

Sulfoglycolipid from the marine brown alga Sargassum hemiphylum.

One kinds of glycolipid (SBI) have been isolated from the marine brown alga Sargassum hemiphyllum (Turn.) Ag. The structures of SBI have been determined as the sodium salt of 1-0-acyl-3-0-(6'-sulfo-alpha-D-quinovopyrannosyl) glycerol (acyl: tetradecanoyl, pentadecanoyl, 11-hexadecenoyl, hexadecanoyl, 10,13-octadecadienoyl, 9-octade cenoyl, 15-metylheptadecanoyl and 11-eicosenoyl 17: 1.5: 19: 153: 1: 19: 1: 2) on the basis of chemical and spectral evidence and GC-MS analysis, respectively. Four constituents of the SBI were new compounds [the sodium salt of 1-0-(11"-hexadecenoyl)-3-0-(6'-sulfo-alpha-D-quinovopyrannosyl) glycerol, the sodium salt of 1-0-(10",13"-octadecadienoyl)-3-0-(6'-sulfo-alpha-D-quinovopyrannosyl) glycerol, and the sodium salt of 1-0-(15"-metylhexadecenoyl)-3-0-(6'-sulfo-alpha-D-quinovopyrannosyl) glycerol, and the sodium salt of 1-0-(11"-eicosenoyl)-3-0-(6'-sulfo-alpha-D-quinovopyrannosyl) glycerol]. All compounds were isolated from marine brown alga for the first time.

China↗

PubMed2001

The effect of electro-acupuncture on motor function recovery in patients with acute cerebral infarction: a randomly controlled trial.

UNLABELLED: The aim of this study is to investigate the effect of electro-acupuncture treatment in acute phase of cerebral infarction on the motor functions. In this randomly controlled trial, 86 patients were allocated to two groups, the experimental group given clinical and electro-acupuncture treatments for a period of 4 weeks, and the control group given clinical treatment plus active and/or passive functional exercise. The result showed that the level of impairment and disability in both groups were improvement according to the Chinese Stroke Scale, Brunnstrom-Fugl-Meyer score, and Barthel Index throughout the study and 3 months after. The motor functions and the activities of daily living (ADL) were improved significantly in the electro-acupuncture group as compared with the control group (P < 0.05). Also, the results showed greater reduction of neurological deficit in the electro-acupuncture group than in the control group. CONCLUSION: Early acupuncture treatment for acute stroke patients may improve motor functions, and consequently the activities of daily living.

Acupuncture Therapy↗

PubMed2000

The functional relevance of NK-cell-mediated upregulation of antigen-specific IgG2a responses.

We have previously shown that activation of NK cells by poly(I:C) or tumor treatment of mice increases the level of antigen-specific IgG2a (1, 2). We have now assessed the functional relevance of this effect of the innate immune system on the specific immune response. We found that the increased IgG2a significantly augments antibody-dependent cellular cytotoxicity mediated by NK cells both in vivo and in vitro. Furthermore, we show that both IgG3 producing plasma cells induced by T-independent antigens and IgG2a plasma cells induced in the presence of activated NK cells may be just as long-lived as plasma cells induced by T-dependent antigens. These results indicate that if NK cells are activated early in the immune response, before T cells are recruited, they could exert long-lasting effects.

Animals↗

PubMed2000

[Improved endocardial border delineation during dobutamine stress echocardiography using the left heart contrast medium BY 963].

UNLABELLED: The interpretation of induced wall motion abnormalities during dobutamine stress echocardiography is affected in the case of impaired image quality. In 48 consecutive patients (mean age 62 +/- 9 years, 32 males, 16 females) with suspected coronary disease undergoing coronary angiography, the transpulmonary contrast agent BY 963 was given i.v. as bolus during dobutamine stress echocardiography (10-40 micrograms kg min, plus max. 1 mg atropine) to analyze improvements in endocardial border delineation. For each of the 16 segments of the left ventricle, the endocardial border delineation was evaluated. Using BY 963 the average number of non-evaluable segments decreased by 58% from 5.2% to 2.2% at rest (p = 0.008) and by 56% from 5.9% to 2.6% at maximal stress (p = 0.003) as compared to the non-contrast study for all patients. In patients with impaired image quality, defined as at least 1 non-evaluable segment at rest without contrast enhancement (N = 14), the number of non-evaluable segments decreased from 19.2% to 8.2% (p = 0.004) at rest and from 19.2% to 9.6% (p = 0.006) at maximal stress. The greatest decrease of non-evaluable segments was seen in the lateral and anterior segments of the apical views (maximum of 80%). The improved endocardial border delineation resulted in an improved agreement between two observers in the interpretation of the dobutamine stress echocardiograms as positive or negative (kappa = 0.38 without contrast, kappa = 0.58 with contrast). Contrast application resulted in a slight improvement of diagnostic accuracy of dobutamine stress echocardiography in the detection of angiographically proven significant coronary artery disease. CONCLUSION: In patients with impaired endocardial border delineation the use of the echo contrast agent BY 963 reduces the number of non-evaluable segments. Improvement of endocardial delineation is greatest for lateral and anterior segments in the apical views.

Aged↗

PubMed2000

Mutagenicity of methyl tertiary butyl ether.

Methyl tertiary butyl ether (MTBE), the main component of oxygenated gasoline, is added to gasoline as an octane enhancer to reduce automotive emissions. We evaluated the mutagenicity of domestic MTBE using the Ames test, unscheduled DNA synthesis (UDS) assay, and NIH/3T3 cell micronucleus test. MTBE did not show any mutagenic potential in the Ames assay (TA98, TA100 strains) with or without rat liver-derived metabolic activation system (S-9). In rat primary hepatocyte UDS assay, a dose-response relationship was observed, which meant that MTBE might damage normal DNA and induce unscheduled DNA synthesis. MTBE did not show positive results in the NIH/3T3 cell micronucleus test. It could be concluded that MTBE has some degree of mutagenicity.

3T3 Cells↗

PubMed2000

Effect of leaded and unleaded gasoline on the mutagenicity of vehicle exhaust particulate matter.

With the removal of lead from gasoline and the use of new technologies, there have been some changes in vehicle emissions. In order to find out if the unleaded gasoline has the ability to reduce the emission of pollutants, leaded and unleaded gasoline were tested on a Santana engine dynamometer under a standard test cycle. The concentrations of hydrocarbons (HC) and carbon monoxide (CO) in emission were analyzed. The extracts of total exhaust particles were also collected and the components were detected by gas chromatography/mass spectrometry (GC/MS). A series of different end point genotoxicity tests, including the Ames test, the single cell gel electrophoresis (SCGE) assay, and micronucleus induction assay, were performed to investigate the mutagenicity in the two kinds of gasoline. We found that unleaded gasoline could reduce the emission of CO and HC and significantly decrease the quantity of vehicle exhaust particulate matter by 60%. As for the component analysis, only 23 kinds of organic substances adsorbed onto the particles were identified in the unleaded gasoline, while 32 kinds of compounds were detected in the leaded gasoline. The genotoxicity tests indicated that both types of gasoline could enhance the number of histidine-independent colonies in the Ames test, cause DNA damage, and increase the frequency of induced micronucleus in the Chinese hamster lung (CHL) cells. For the same particle weight, no difference was found between their mutagenicity. Because of the decrease in the emission of CO, HC, and particles in unleaded gasoline, this gasoline has some benefits for the environment and human health.

Animals↗

PubMed2000

[A clinical analysis of combination treatment with brachytherapy and external radiation, plus chemotherapy for the treatment of esophageal cancer].

OBJECTIVE: To analyse the value of various combinations of treatment for esophageal cancer. METHODS: One hundred twenty cases of esophageal cancer were randomly divided into four groups, 30 cases in each group. Group I was treated with external radiation (RT) alone; group II, with RT plus brachytherapy; group III with RT plus chemotherapy, and group IV with RT plus brachytherapy and chemotherapy. RT with 60Co was given 2 Gy daily, 5 times a week, with a total dose of 60-74 Gy. Brachytherapy was given 6-8 Gy once weekly with a total dose of 18-24 Gy. Chemotherapy with carboplatin was given 100 mg/day, five days a week at first and fifth week. RESULTS: The 1, 2, 3-year survival rate in group II, III and IV was higher than that in group I (P < 0.05). The 3-year survival rate of group I-IV patients was 13.3%, 36.7%, 40.0%, 46.7%, respectively. More patients died of cancer recurrence and progression in group I than in any of the other 3 groups of patients (P < 0.05). However, the frequency of distant metastasis was not significantly different. CONCLUSION: The combination treatment with external radiation, brachytherapy and chemotherapy can improve the local control of tumor growth and the survival rate in esophageal cancer patients.

Adenocarcinoma↗

PubMed1999

Characterization of a plasma membrane calcium oscillator in rat pituitary somatotrophs.

In excitable cells, oscillations in intracellular free calcium concentrations ([Ca(2+)](i)) can arise from action-potential-driven Ca(2+) influx, and such signals can have either a localized or global form, depending on the coupling of voltage-gated Ca(2+) influx to intracellular Ca(2+) release pathway. Here we show that rat pituitary somatotrophs generate spontaneous [Ca(2+)](i) oscillations, which rise from fluctuations in the influx of external Ca(2+) and propagate within the cytoplasm and nucleus. The addition of caffeine and ryanodine, modulators of ryanodine-receptor channels, and the depletion of intracellular Ca(2+) stores by thapsigargin and ionomycin did not affect the global nature of spontaneous [Ca(2+)](i) signals. Bay K 8644, an L-type Ca(2+) channel agonist, initiated [Ca(2+)](i) signaling in quiescent cells, increased the amplitude of [Ca(2+)](i) spikes in spontaneously active cells, and stimulated growth hormone secretion in perifused pituitary cells. Nifedipine, a blocker of L-type Ca(2+) channels, decreased the amplitude of spikes and basal growth hormone secretion, whereas Ni(2+), a blocker of T-type Ca(2+) channels, abolished spontaneous [Ca(2+)](i) oscillations. Spiking was also abolished by the removal of extracellular Na(+) and by the addition of 10 mM Ca(2+), Mg(2+), or Sr(2+), the blockers of cyclic nucleotide-gated channels. Reverse transcriptase-polymerase chain reaction and Southern blot analyses indicated the expression of mRNAs for these channels in mixed pituitary cells and purified somatotrophs. Growth hormone-releasing hormone, an agonist that stimulated cAMP and cGMP productions in a dose-dependent manner, initiated spiking in quiescent cells and increased the frequency of spiking in spontaneously active cells. These results indicate that in somatotrophs a cyclic nucleotide-controlled plasma membrane Ca(2+) oscillator is capable of generating global Ca(2+) signals spontaneously and in response to agonist stimulation. The Ca(2+)-signaling activity of this oscillator is dependent on voltage-gated Ca(2+) influx but not on Ca(2+) release from intracellular stores.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1999

Expression of Ca(2+)-mobilizing endothelin(A) receptors and their role in the control of Ca(2+) influx and growth hormone secretion in pituitary somatotrophs.

The expression and coupling of endothelin (ET) receptors were studied in rat pituitary somatotrophs. These cells exhibited periods of spontaneous action potential firing that generated high-amplitude fluctuations in cytosolic calcium concentration ([Ca(2+)](i)). The message and the specific binding sites for ET(A), but not ET(B), receptors were found in mixed pituitary cells and in highly purified somatotrophs. The activation of these receptors by ET-1 led to an increase in inositol 1,4,5-trisphosphate production and the associated rise in [Ca(2+)](i) and growth hormone (GH) secretion. The Ca(2+)-mobilizing action of ET-1 lasted for 2-3 min and was followed by an inhibition of action potential-driven Ca(2+) influx and GH secretion to below the basal levels. As in somatostatin-treated cells, the ET-1-induced inhibition of spontaneous electrical activity and Ca(2+) influx was accompanied by the inhibition of adenylyl cyclase and by the stimulation of inward rectifier potassium current. In contrast to somatostatin, ET-1 did not inhibit voltage-gated Ca(2+) channels. During prolonged agonist stimulation a gradual recovery of Ca(2+) influx and GH secretion occurred. In somatotrophs treated with pertussis toxin overnight, the ET-1-induced Ca(2+)-mobilizing phase was preserved, but it was followed immediately by facilitated Ca(2+) influx and GH secretion. Both somatostatin- and ET-1-induced inhibitions of adenylyl cyclase activity were abolished in pertussis toxin-treated cells. These results indicate that the transient cross-coupling of Ca(2+)-mobilizing ET(A) receptors to the G(i)/G(o) pathway in somatotrophs provides an effective mechanism to change the rhythm of [Ca(2+)](i) signaling and GH secretion during continuous agonist stimulation.

Adenylate Cyclase Toxin↗

PubMed1999

Contributions to gene activation by multiple functions of Bicoid.

Bicoid is a Drosophila morphogenetic protein required for the development of anterior structures in the embryo. To gain a better understanding of how Bicoid works as a transcriptional activator, we systematically analysed various functions of Bicoid required for gene activation. We provide evidence suggesting that Bicoid is an intrinsically weak activator. First, our biochemical experiments demonstrate that the Bicoid-DNA complexes are very unstable, suggesting a weak DNA-binding function of Bicoid. This idea is further supported by our experiments demonstrating that the same number of LexA-Bicoid fusion molecules can activate transcription more effectively from LexA sites than from Bicoid sites. Secondly, we demonstrate that transcriptional activation by the weak activator Bicoid is readily influenced by the local enhancer environment. These influences are decreased when the Bicoid function is enforced by attaching to it either a known dimerization domain or the strong activation domain VP16. VP16 can also compensate for the loss of some Bicoid sites in an enhancer element. Our experiments demonstrate that the outcome of transcriptional activation by Bicoid is determined by multiple weak functions that are interconnected, a finding that can further help us to understand how this morphogenetic protein achieves its molecular functions.

Base Sequence↗

PubMed1999

The mechanism of activation of NK-cell IFN-gamma production by ligation of CD28.

We have investigated the mechanism by which anti-CD28 antibodies activates IFN-gamma production by murine NK cells. These studies reveal that engagement of CD28 alone by this antibody is a poor activator of this cytokine response. Effective stimulation requires simultaneous ligation of the receptor for Fc (FcgammaRIII, CD16) which on its own is also a poor inducer of murine NK cells. The mechanism by which immobilized anti-CD28 increases IFN-gamma mRNA abundance involves both upregulation of transcription as well as induction of mRNA stabilization. However, the elevation of transcription is not as evident as that induced by IL-12 which, in contrast, does not induce message stabilization. Thus ligation of CD28 in the presence of IL-12 results in a synergistic increase in production of the cytokine. Using this assay we have also determined that immobilized anti-CD28 cannot induce resting NK cells to produce IFN-gamma. In contrast, the same cells can be induced by BCL1-C11 tumor cells that express high amounts of the CD28 ligand, B7-2. These studies provide important insights into the ability of cells bearing counter-receptor for CD28 to activate NK cell-cytokine production in vivo.

Animals↗

PubMed1999

Differential regulation of transcription termination occurring at two different sites on the micro-delta gene complex.

The progression of polymerases across the micro-delta Ig heavy chain gene complex is characterized by two termination events occurring at different sites on the transcription unit and at different times during B cell differentiation. We have utilized two mouse strains to analyze the regulatory determinants for these events in primary B cells. In the transgenic pmicro.microdeltaRatt strain a 1160 bp intervening DNA segment (the att site) has been inverted. This mutation results in the abrogation of transcription termination that occurs in early B cells. Using a novel method that takes advantage of an internal ribosome entry site we have further restricted the size of the segment that is needed for inducing transcription termination in transfectants. This 200 bp termination-inducing sequence operates in tumor equivalents of early but not mature B cells and the activity is correlated with differential binding of nuclear proteins. To explore the regulatory basis for the change in site of transcription termination upon B cell activation we have examined the microS-/- deletion mutant strain in which the microS poly(A) site has been eliminated. The results suggest that polyadenylation at the microS site plays a dominant but not exclusive role in regulating transcription termination in activated B cells.

Animals↗