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Y Ni

Publications and source records attributed to Y Ni.

At least 37 records · Page 2Linked to original sources
PubMed2001

MRI contrast enhancement of necrosis by MP-2269 and gadophrin-2 in a rat model of liver infarction.

RATIONALE AND OBJECTIVES: The mechanisms of action leading to specific localization of necrosis-avid contrast agents (NACAs) such as gadophrin-2 are not well defined. It has been suggested recently that agents with a high degree of serum albumin binding may also serve as NACAs by virtue of nonspecific hydrophobic interactions. The present MRI-histomorphology correlation study was conducted to verify the likelihood of the proposed albumin-binding mechanism by comparing an albumin-binding blood pool agent, MP-2269, with gadophrin-2 in a rat model of reperfused liver infarction. METHODS: Reperfused infarction in the right liver lobe was surgically induced in six rats. Serial T1-weighted MRI was performed before and after intravenous injection of MP-2269 at 0.05 mmol/kg and repeated in the same rats 24 hours later after intravenous injection of gadophrin-2 at the same dosage (0.05 mmol/kg). The MR images were matched with corresponding histomorphological findings. The signal intensity and contrast ratio of infarcted and normal hepatic lobes were quantified and compared between the two agents during the postcontrast course. RESULTS: Before contrast, the infarcted lobe was indiscernible from normal liver on T1-weighted MRI. Shortly after injection of both MP-2269 and gadophrin-2, a negative contrast occurred between infarcted and normal liver because of a strong liver signal intensity enhancement and an inferior uptake in the necrotic liver. On delayed phase (>60 minutes), a necrosis-specific contrast enhancement (contrast ratio 1.6) developed with gadophrin-2 but not with MP-2269. The MR images matched well with corresponding histomorphological findings. CONCLUSIONS: Although both MP-2269 and gadophrin-2 feature an albumin-binding capacity, only gadophrin-2 displayed a persistent necrosis-specific contrast enhancement in the rat model of reperfused liver infarction. Therefore, the role of albumin binding in the mechanisms of NACAs should be reevaluated.

Animals↗
PubMed2001

[Preferential flow and its effect on solute migration in soil].

The characteristics of soil preferential flow and the preferential migrate in soil for non-absorptive bromide and nitrate ions were studied. With undisturbed and packed soil columns, the results showed that soil preferential flow was characterized with preferential breakthrough, non-symmetric breakthrough curve, lateral infiltration, tailing and so on. The preferential breakthrough for Br- was 24 hours after it was applied, and the leachate volume was only 0.04 times as-much as the pore volumes. The preferential flow for Br- accounted for 26% of total flux in the undisturbed soil columns. But the accumulative leachate mass for Br- resulted from the preferential flow were 86.7% of total accumulative leachate mass, showing that the soil preferential flow accounted for relative small ratio of the flux, but caused relative much more solute transference. NO3- was moved down rapidly by preferential flow at only one time as large as pore volumes, and got 11% of the applied amount, respectively. As a result of the preferential flow, the lateral infiltration flow enabled Br- and NO3- rapidly distribute and diffuse into the deeper soil.

Bromine↗
PubMed2001

[Micro -- ecological investigation of burn wound infection].

OBJECTIVE: To analyze the epidemic tendency of the bacteria causing burn wound infection, and to explore the influencing factors. METHODS: Bacterial ecology on burn wound was investigated in 210 cases of burn patients admitted to our hospital from January 1999 to December 2000, and the results were compared to those done in the 1970s, 1980s and 1990s. RESULTS: Since 1999, G(+)cocci increased obviously (52.17%) when compared with those of the past three decades (P < 0.01), while G(minus sign) bacilli decreased significantly (46.48%, P < 0.01). The ratio of Pseudomonas aeruginosa in recent two years was evidently lower than those in the early 1970s and 1990s (P < 0.01) while the ratio of staphylococcus aureus was much higher than those in the middle of 1980s and 1990s (P < 0.01), in which methacillin -- resistant Staphylococcus aureus (MRSA) accounted for 85% or so, which increased significantly than those in the middle of 1980s and the beginning of 1990s (P < 0.01) with an increasing tendency. CONCLUSION: The increasing tendency of Staphylococcus aureus in our unit for the recent two years might closely be related to the preferential application of Imipenem in burn infection control. Furthermore, the ratio of MRSA in Staphylococcus aureus could not be lowered by vancomycin.

Anti-Bacterial Agents↗
PubMed2001

[Correction for the spectral interferences of rare-earth matrix to the determination of calcium by spectral fitting matrix projection-Kalman filter method].

The spectral interferences of trace elements from high purity rare earth will seriously affect the analytical accuracy in the ICP-AES analysis. In this work, spectral fitting matrix projection-Kalman filter method was developed and applied to correction of spectral interferences produced by rare earth matrix peaks with simple shapes in determination of calcium, and it was applied to correct spectral interferences caused by terbium oxide and dysprosium oxide respectively, and satisfactory results were obtained.

Calcium↗
PubMed2000

Mechanisms of apoptosis in rat cerebellar granule cells induced by hydroxyl radicals and the effects of EGb761 and its constituents.

In this study investigation is made on whether oxidative stress produced by treatment with hydroxyl radicals can induce apoptosis in rat cerebellar granule cells. The protective effects of Ginkgo biloba extract (EGb761) and its active constituents against apoptosis are also examined. The results show that hydroxyl radicals generated by the Fenton reaction induced apoptosis in cerebellar granule cells, which was associated with the decrease in the Bcl-2 mRNA level and the increase in the protein levels of the transcription factors Fos and Jun. Moreover, hydroxyl radicals induced time-dependent lipid peroxidation in cells and caused the changes in the sulfhydryl group binding sites on the membrane proteins. Hydroxyl radicals may induce apoptosis via different signaling pathways. EGb761 attenuated these changes and its different constituents showed different effects. The total flavonoid component of EGb761 and a mixture of flavonoids and terpenes protected cerebellar granule cells from oxidative damage and apoptosis induced by hydroxyl radicals. Total terpenes of EGb761 did not protect against apoptosis. Flavonoids and terpenes did not show a synergistic effect in this regard.

Animals↗
PubMed2000

Regulation of protein kinase D by multisite phosphorylation. Identification of phosphorylation sites by mass spectrometry and characterization by site-directed mutagenesis.

Activation of the serine/threonine kinase, protein kinase D (PKD/PKC mu) via a phorbol ester/PKC-dependent pathway involves phosphorylation events. The present study identifies five in vivo phosphorylation sites by mass spectrometry, and the role of four of them was investigated by site-directed mutagenesis. Four sites are autophosphorylation sites, the first of which (Ser(916)) is located in the C terminus; its phosphorylation modifies the conformation of the kinase and influences duration of kinase activation but is not required for phorbol ester-mediated activation of PKD. The second autophosphorylation site (Ser(203)) lies in that region of the regulatory domain, which in PKC mu interacts with 14-3-3tau. The last two autophosphorylation sites (Ser(744) and Ser(748)) are located in the activation loop but are only phosphorylated in the isolated PKD-catalytic domain and not in the full-length PKD; they may affect enzyme catalysis but are not involved in the activation of wild-type PKD by phorbol ester. We also present evidence for proteolytic activation of PKD. The fifth site (Ser(255)) is transphosphorylated downstream of a PKC-dependent pathway after in vivo stimulation with phorbol ester. In vivo phorbol ester stimulation of an S255E mutant no longer requires PKC-mediated events. In conclusion, our results show that PKD is a multisite phosphorylated enzyme and suggest that its phosphorylation may be an intricate process that regulates its biological functions in very distinct ways.

Alanine↗
PubMed2000

Phosphorescent oxygen sensors utilizing sulfur-nitrogen-phosphorous polymer matrixes: synthesis, characterization, and evaluation of poly(thionylphosphazene)-b-poly(tetrahydrofuran) block copolymers

We examine the use of thionylphosphazene-based block copolymers as matrixes for oxygen sensor applications. Poly(aminothionylphosphazene)-b-poly(tetrahydrofuran) (PATPy-PTHFx) block copolymers were prepared via reaction of ring-opened poly(chlorothionylphosphazene) with THF and subsequently with excess n-butylamine (to form PBATPy-PTHFx) or methylamine (to form PMATPy-PTHFx). The block copolymers were characterized by NMR, gel permeation chromatography, and differential scanning calorimetry. Films of PBATPy-PTHFx block copolymers containing platinum octaethylporphyrin or [Ru(dpp)3]Cl2 (dpp = 4,7-diphenyl-1,10-phenanthroline) as the oxygen-sensitive chromophore were prepared, and time-scan experiments were carried out to determine the diffusion coefficients, Do2, and solubilities, So2, of oxygen therein. Despite microphase separation, the data fit well to a simple Fick's law description of oxygen diffusion and gave Do2 values smaller than that for the n-butylamino-substituted PBATP635. For films freshly annealed above the melting point of PTHFx, the Do2 values were 35-50% (dye-dependent) larger than after aging 3 days at room temperature. Films with [Ru(dpp)3]Cl2 as the dye were evaluated as media for phosphorescent pressure-sensing. The dye-containing polymer films exhibit linear Stern-Volmer-like plots, even at high dye concentrations, as well as good photostability, and significantly higher sensitivity to oxygen quenching than simple mixtures of the analogous homopolymers.

Journal Article↗
PubMed2000

Hydrogen peroxide-induced oxidative damage and apoptosis in cerebellar granule cells: protection by Ginkgo biloba extract.

The ability of oxidative stress to induce apoptosis and the protective effects of Ginkgo biloba extract (EGb761) against this induction were studied in cultures of rat cerebellar granule cells. Cells were exposed to oxidative stress by treatment with 50 microm hydrogen peroxide+100 microm ferrous sulphate which generates hydroxyl radicals by Fenton reaction. Both morphological observation and biochemical analysis revealed that H(2)O(2)/FeSO(4)treatment induced apoptotic cell death in cerebellar granule cells, which was characterized by chromatin condensation and DNA fragmentation. During this process, the fluidity of the cell membrane decreased markedly, and the conformation of membrane proteins altered significantly. Pretreating cerebellar granule cells with the antioxidant EGb761 (Ginkgo biloba extract) effectively attenuated oxidative damage induced by H(2)O(2)/FeSO(4), and prevented cells from apoptotic cell death. The results suggested that EGb761 might be used as a potential drug for neuronal diseases associated with the excessive production of reactive oxygen species.

Animals↗
PubMed2000

Treatment of VX2 liver tumor in rabbits with "wet" electrode mediated radio-frequency ablation.

Radio-frequency ablation (RFA) has been considered as an alternative therapy for liver tumors. A "wet" electrode with interstitial infusion of hypertonic saline was tested for the RFA of liver tumor in rabbits. Seventy-eight liver tumors ( 1.5 to 3.0 cm) were induced in 41 rabbits by VX2 carcinoma implantation. Fifty-one tumors in 27 rabbits were treated with RFA. Under laparotomy, the RF energy was delivered while 5 % saline was infused through the electrode into the tumor at 1 ml/min. Six rabbits with 12 tumors were treated with only intratumoral 5 % saline infusion without RFA. Another 8 rabbits with 15 tumors received sham operation as untreated controls. The efficacy of the therapy was evaluated with survival rate, MRI, microangiography, and histopathology. In the RFA group, 6 rabbits survived longer than 6 months (absolute eradication rate 22.2 %); 12 rabbits were found free of viable tumor at the moment when they were sacrificed (relative eradication rate 44.4 %); 9 rabbits showed local tumor relapse and/or lung metastasis 2-10 weeks after ablation (recurrent rate 33.3 %). In control groups of saline infusion and sham operation, all 14 rabbits died within 3 months (mortality rate 100 %). Three-month survival rates between RFA group and control groups were significantly different (p < 0.05). Findings of MRI, microangiography, and histology supported these outcomes. Radical treatment of liver malignancy in rabbits is possible with the present modified RFA technique. Its clinical usefulness has to be further proven.

Animals↗
PubMed2000

A novel "cooled-wet" electrode for radiofrequency ablation.

In the light of growing demands for improved applicability of radiofrequency ablation (RFA), recently we have developed a novel "cooled-wet" electrode by taking the advantages of both internally cooled and saline-enhanced electrodes. The efficacy of the electrode was evaluated in both ex vivo and in vivo liver RFA under both low and high power output levels. The ablation volume created with the "cooled-wet" electrode appeared to be much larger than that reported up to now with the use of other monopolar electrodes. The mechanisms on how this device optimizes the RF energy delivery are also discussed.

Animals↗
PubMed2000

Some nutritional and functional properties of defatted wheat germ protein.

Defatted wheat germ protein (DWGP) was isolated by alkaline extraction at pH 9.5 and subsequent isoelectric precipitation at pH 4.0, and its nutritional and functional properties were studied. The results showed that the amino acid content of defatted wheat germ was as high as 26.793 g/100 g, and the contents of eight essential amino acids were all relatively high. The isoelectric point of DWGP was 4.0. When pH >6.0, the DWGP had high solubility with a nitrogen solubility index of 70%. The emulsifying activity and emulsifying stability of DWGP were similar to those of bovine serum albumin and a little higher than those of casein. DWGP had good foaming capacity, but its foaming stability (FS) was not very good. However, the FS of DWGP can be improved through physical, chemical, or enzymatic methods. Moreover, DWGP had excellent water retention (WR); especially at pH 8.0 and a temperature of 70 degrees C, the WR of DWGP was the highest at 229.4%. DWGP offers is a potential source of functional protein isolate for possible food applications.

Chemical Phenomena↗
PubMed2000

New approach for preparation of 2,3,7-trisubstituted 3,4-dihydroisoquinolinone libraries on solid phase.

In an attempt to prepare 7-substituted 3,4-dihydroisoquinolinone family of compounds, we observed an unexpected decarboxylation. The reaction of 4-nitrohomophthalic anhydride with a Schiff base formed on solid support leads to the formation of core structure. LC-MS and 1H NMR analysis confirmed the structure of unexpected intermediate. A library of 38,400 compounds was produced using this new synthetic approach.

Anhydrides↗
PubMed2000

A comparative study on validation of a novel cooled-wet electrode for radiofrequency liver ablation.

RATIONALE AND OBJECTIVES: A cooled-wet electrode has been developed for radiofrequency ablation (RFA) that allows simultaneous internal-cooling perfusion ("cooled") and interstitial hypertonic saline infusion ("wet"). The present comparative study was conducted to validate this new device for the increased coagulation volume in RFA. METHODS: Under low-power (50 W, groups A through F) and high-power (90 W, groups A' through F') control modes, 240 RFA lesions were created on excised beef liver to compare the cooled-wet electrode with other monopolar electrodes. The experimental regimens were as follows: groups A and A', conventional RF electrode; groups B and B', cooled electrode; groups C and C', wet electrode; groups D and D', cooled-wet electrode; groups E and E', cooled-wet electrode but suspended wet function; and groups F and F', cooled-wet electrode but suspended cooled function. The ablation efficacy was evaluated by comparing the lesion sizes as well as parameters of impedance, power output, current, and tip temperature. RESULTS: With lower impedance and tip temperature but higher power output, the lesion size in groups D (4.90 +/- 0.60 cm) and D' (6.6 +./- 0.99 cm) was significantly larger than that in other groups. CONCLUSIONS: The use of the cooled-wet electrode could efficiently increase the lesion size for liver ablation.

Animals↗
PubMed2000

Specificity and prevalence of natural bovine anti-alpha galactosyl (Galalpha1-6Glc or Galalpha1-6Gal) antibodies.

Immunity against the carbohydrate components of microorganisms mediated by antibodies is an important part of host defenses. Humans and closely related primates, but not other mammals, possess natural anti-Galalpha1-3Gal antibodies which also, although less avidly, react with melibiose (Galalpha1-6Glc). Using an enzyme-linked immunosorbent assay (ELISA) with melibiose-bovine serum albumin as an antigen, we analyzed bovine anti-alpha galactosyl antibodies with respect to specificity and distribution in individual animals. Inhibition assays showed that melibiose was the strongest inhibitor, followed equally by stachyose (Galalpha1-6Galalpha1-6Glcbeta1-2Fru) and raffinose (Galalpha1-6Glcbeta1-2Fru) and then by Galbeta1-6Gal, Gal, and Galalpha1-2Gal. Others, including Galalpha1-3Gal and Galalpha1-4Gal, only exhibited minor inhibition. Thus, these bovine anti-alpha galactosyl antibodies appeared to preferentially react with Galalpha1-6Glc or Galalpha1-6Gal. The distinction of this specificity from that (Galalpha1-3Gal) of human antibodies was further demonstrated by the poor reaction of bovine serum to the Galalpha1-3Gal antigen in comparison to human serum. All 27 healthy bovine serum samples of the three age groups (newborn, calf, and adult) tested contained such antibodies with titers increasing with age. The antibodies purified by affinity chromatography using a melibiose-agarose column were mainly of the immunoglobulin G (IgG) isotype with a concentration of >23 microg/ml in most samples. IgG1 was found to be the primary antimelibiose IgG isotype in all age groups by isotype-specific ELISA, but a significant increase in IgG2, an isotype more related to innate immunity, was observed in calves and adults, compared to newborns. The purified antibodies reacted with the type II bovine strain of Streptococcus agalactiae, a common pathogen of bovine mastitis. Thus, these anti-Galalpha1-6Glc or Galalpha1-6Gal antibodies in cattle might be involved in defense against microbes bearing this or the related epitopes.

Age Factors↗
PubMed1999

VEGI, a new member of the TNF family activates nuclear factor-kappa B and c-Jun N-terminal kinase and modulates cell growth.

Recently a new member of the human tumor necrosis factor (TNF) family named as VEGI was reported. However, very little is known about the biological activities displayed by this cytokine. In this report, we show that in myeloid cells VEGI activated the transcription factor kappa B (NF-kappa B) as determined by the electrophoretic mobility shift assay, induced degradation of I kappa B alpha, and nuclear translocation of p65 subunit of NF-kappa B. VEGI also activated NF-kappa B-dependent reporter gene expression. In addition, VEGI activated c-Jun N-terminal kinase. When examined for growth modulatory effects, VEGI inhibited the proliferation of breast carcinoma (MCF-7), epithelial (HeLa), and myeloid (U-937 and ML-1a) tumor cells; and activated caspase-3 leading to PARP cleavage. VEGI-induced cytotoxicity was potentiated by inhibitors of protein synthesis. VEGI also induced proliferation of normal human foreskin fibroblast cells. The activity of VEGI could neither be neutralized by antibodies against TNF, nor could it compete with TNF binding, indicating that the activity of VEGI is not due to TNF and it binds to a distinct receptor. These results suggest that VEGI, a new member of the TNF family, has a signaling pathway similar to TNF and is most likely a multifunctional cytokine.

Base Sequence↗
PubMed1999

Palmitoylation of the recombinant human A1 adenosine receptor: enhanced proteolysis of palmitoylation-deficient mutant receptors.

Palmitoylation of the recombinant human A(1) adenosine receptor (A(1)AR) expressed in HEK-293 cells is demonstrated by showing that hexahistidine (His(6))/Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys (FLAG) (H/F) A(1)ARs, purified to homogeneity from cells metabolically labelled with [(3)H]palmitate, incorporate tritium into a 38-42 kDa receptor glycoprotein. The amount of palmitoylation is not affected by incubation of cells with the A(1)AR-selective agonist N(6)-cyclopentyladenosine (CPA). A(1)AR palmitoylation is abolished by treatment with neutral hydroxylamine or by mutation of Cys-309 to Ala (C(309)-->A). Based on Western blotting and pulse-chase experiments with [(35)S]methionine, at least 90% of wild-type receptors are palmitoylated and turn over with a t1/2 of 6.4 h. Of the C(309)-->A mutated receptors, 40% appear to turn over like wild-type receptors, with a t1/2 of 7.1 h, and 60% appear to be rapidly cleaved to form a 25 kDa receptor fragment that turns over with a t1/2 of 0.8 h. In HEK-293 cell lines expressing similar numbers of wild-type or C(309)-->A mutant A(1)Rs, there is little difference in the kinetics of CPA-induced receptor internalization (1 h), down-regulation (24 h), inhibition of forskolin-stimulated cAMP accumulation, or activation of co-transfected G-protein-activated inward rectifier K(+)/cardiac inward rectifying K(+) (GIRK1/CIR K(+)) channels. Also unaffected by palmitoylation is guanosine 5'-[gamma-thio]-triphosphate ([S]GTP)-sensitive binding to membranes by the agonist (125)I-labelled aminobenzyladenosine. The results suggest that palmitoylation has little effect on receptor-effector coupling, agonist-induced internalization or down-regulation. We speculate that palmitoylation may divert newly synthesized A(1)ARs from a pathway leading to rapid degradation.

Adenosine↗
PubMed1999

Noninvasive measurements of infarct size after thrombolysis with a necrosis-avid MRI contrast agent.

BACKGROUND: Gadophrin-2 is a new MRI contrast agent with high affinity for necrotic myocardium. The aim of the study was to evaluate whether noninvasive measurements of infarct size after thrombolysis are possible with gadophrin-2-enhanced MRI. METHODS AND RESULTS: Coronary artery thrombosis was induced in 3 groups of dogs by the copper-coil technique. Thrombolytic therapy together with aspirin and heparin was initiated after 90 minutes of occlusion. One day (group A), 2 days (group B), or 6 days (group C) after infarction, gadophrin-2 was injected intravenously (50 micromol. kg-1). In vivo T1-weighted segmented turbo-FLASH, in vivo T2-weighted segmented half-Fourier turbo spin echo (HASTE), and T1- and T2-weighted spin-echo MRI of the excised heart were performed 24 hours after gadophrin-2 injection. Regions of strong enhancement were observed on T1-weighted images. Planimetry of short-axis MR images and of corresponding triphenyltetrazolium chloride (TTC)-stained left ventricular (LV) slices showed a close correlation between the enhanced areas and TTC-negative areas for both in vivo (r2=0.98, P<0.0001; mean difference, 0.9+/-2.0% [SD] of the LV volume [LVV]) and postmortem (r2=0.99, P<0.0001; mean difference, 0.9+/-1.4% of LVV) measurements. T2-weighted images overestimated the infarct size by 8.1+/-5.4% of LVV. The mean infarct size was 10.8+/-11.6% of LVV (group A), 22.4+/-11.7% (group B), and 5.1+/-9.3% (group C). CONCLUSIONS: In this animal model, in vivo gadophrin-2-enhanced MRI could precisely determine infarct size after thrombolytic therapy. This technique may be very useful for the noninvasive evaluation of infarct size after reperfusion for AMI.

Animals↗