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Yi Xu

Publications and source records attributed to Yi Xu.

At least 73 records · Page 4Linked to original sources
PubMed2004

Step-height measurement by means of a dual-frequency interferometric confocal microscope.

A novel instrument, the dual-frequency interferometric confocal microscope (DICM), which facilitates the measurement of step features, is investigated. It combines the advantages of the high resolution (subnanometer) of heterodyne interferometry and the relatively large measurement range (approximately 5 microm) of confocal microscopy. The axial response curves of the confocal microscopy system are compared in experiments in which microscopic objects with various numerical apertures and magnifications are used. The results prove that the variation in light intensity is enough to permit discrimination of different orders of interference fringes. The DICM has been successfully utilized to measure the step height of a standard mask, and the experimental results agree well with those measured by scanning probe microscopes. The results also show that the system has good repeatability, with a maximum deviation of 5 nm.

Journal Article↗
PubMed2004

Cardioprotection by chronic estrogen or superoxide dismutase mimetic treatment in the aged female rat.

Aging and estrogen deficiency increase the risk for developing cardiovascular disease (CVD). Oxidative stress has also been implicated in the pathophysiology of CVD and in ischemia-reperfusion (I/R) injury. We tested the hypothesis that chronic in vivo estrogen treatment or superoxide inhibition with the SOD mimetic EUK-8 improves cardiac functional recovery after I/R in the aged female rat. Sprague-Dawley rats (12-14 mo) were used as follows: intact (n = 6), ovariectomized + placebo (OVX, n = 6), OVX + EUK-8 (EUK-8, 3 mg/kg, n = 6), and OVX + estrogen (1.5 mg/pellet, 60 days release, n = 6). Perfused isolated hearts were subjected to global ischemia (25 min) followed by reperfusion (40 min). Functional recovery after I/R and myocardial protein expression of NADPH oxidase (p22, p67, and gp91(phox)), inducible nitric oxide synthase (NOS), endothelial NOS, and SOD1, as well as nitrotyrosine levels (as a marker for peroxynitrite), were assessed. Compared with OVX, EUK-8 and estrogen markedly improved functional recovery after I/R, which was associated with a decrease in NADPH oxidase expression and nitrotyrosine staining. However, estrogen increased inducible NOS expression, whereas EUK-8 had little effect. There were no significant changes in endothelial NOS and SOD1 expression among the groups. These results indicate that EUK-8 and estrogen improved cardiac recovery after I/R. Given the controversy surrounding hormone replacement therapy, EUK-8 may be an alternative to estrogen in protecting those at risk for myocardial ischemia in the aging population.

Aging↗
PubMed2004

[Safety and short-term results of stent-assisted angioplasty for the treatment of intracranial arterial stenosis].

OBJECTIVE: To evaluate the safety and short-term outcome of endovascular stent-assisted angioplasty for the treatment of intracranial arterial stenosis. METHODS: Angioplasty and stent placement were administered to treat 46 patients with lesions of atherosclerotic intracranial stenosis, including 16 lesions of basilar artery, 12 of vertebral artery, 13 of internal carotid artery and 9 of middle cerebral artery. RESULTS: Technical success was achieved in 49 of 50 vessels (98%), with no procedure-related death or cerebral ischemic attack. Extracranial internal carotid artery dissection occurred in 1 patient and was successfully treated with a self-expand stent. One patient had subarachnoid hemorrhage because of perforation by microwire with no permanent neurologic deficit, and another 2 patients had groin hematoma. Angiographic examination immediately after stenting revealed that the stenosis rate was significantly reduced (72.4% +/- 12.3% vs 10.6% +/- 7.8%). There was no cerebral ischemic attack in the 37 patients who were clinically followed up (6 - 18 months, mean of 8.5 months). CONCLUSION: Angioplasty and stenting for the treatment of intracranial stenosis is safe and feasible, and it may be favorable for decreasing the incidence of ischemic attack.

Aged↗
PubMed2004

Effects of chronic PGHS-2 inhibition on PGHS-dependent vasoconstriction in the aged female rat.

OBJECTIVE: In menopause, aging and decreased estrogen levels are risk factors contributing to impaired vascular function. Previously, in a young ovariectomized rat model, we demonstrated an increase in prostaglandin H synthase (PGHS)-dependent vasoconstriction that could be prevented by estrogen replacement. Subsequently, we found that, with aging, estrogen acts through suppression of the PGHS-2 isoform. HYPOTHESIS: Chronic PGHS-2 inhibition reduces PGHS-dependent vasoconstriction in aging. METHODS: Ovariectomized, aged (12 months) Sprague-Dawley rats were treated with a placebo (n=7), or the PGHS-2 inhibitor (NS-398, s.c. 3 mg/kg) for 1 week (n=6) or 4 weeks (n=6). Methacholine (endothelium-dependent dilator) and phenylephrine (adrenergic constrictor) were used to assess vascular function in the absence or presence of the nonselective PGHS inhibitor, meclofenamate (1 micromol/l) or the specific PGHS-2 inhibitor NS-398 (10 micromol/l). RESULTS: One week of chronic PGHS-2 inhibition abolished a PGHS-dependent shift in methacholine-induced relaxation, while modulation was still observed in phenylephrine constriction. Surprisingly, 4 weeks of PGHS-2 inhibition enhanced PGHS-dependent modulation of vasoconstriction (P<0.05). PGH2/thromboxane inhibition (U-51605, 50 micromol/l) mimicked the results observed with PGHS inhibition among the groups. PGHS-2 expression increased with chronic PGHS-2 inhibition compared to control (P<0.05). CONCLUSIONS: Our data indicate a paradoxical increase in PGHS-dependent vasoconstriction and PGHS-2 expression with prolonged inhibition of PGHS-2 activity. Hence, inhibitors of PGHS-2 activity may not be beneficial in counteracting the vascular dysfunction seen with aging and menopause.

Animals↗
PubMed2004

In vitro culturing and characteristics of transit amplifying epithelial cells from human prostate tissue.

The prostatic epithelium is functionally organized in stem cell units. This unit consists of a slow turn over stem cell within the basal epithelial layer which can replenish itself and provide progeny which differentiate down either a neuroendocrine or exocrine pathway. The maturation along the exocrine pathway initially involves transit amplifying cells within the basal layer proliferating and subsequently the progeny maturing into intermediate cells. These intermediate cells migrate into the luminal layer where they terminally differentiate into non-proliferative secretory luminal cells which express prostate specific differentiation markers, like PSA. A growing body of experimental evidence has identified the proliferating transit amplifying/intermediate cells as the cells of origin for the common prostatic adenocarcinomas. Using a series of growth characteristics, and mRNA and protein markers, we have validated that primary cultures can be established in serum free defined media from surgically resected human prostates which are composed of essentially pure population of transit amplifying cells. At each serial passage, the subsequent cultures undergo enhanced maturation into intermediate cells and by the 7-10th passage these cells eventually lose their proliferative ability. This study validates that these cells are a useful and relevant system for the determination of molecular events involved in prostatic carcinogenesis.

Androgens↗
PubMed2004

Biocatalytic resolution of glycidyl aryl ethers by Trichosporon loubierii : cell/substrate ratio influences the optical purity of (R) - epoxides.

Glycidyl aryl ethers were resolved by using lyophilized cells of Trichosporon loubierii ECU1040 having epoxide hydrolase activity. The activity and enantioselectivity depended on the structure of the aryl group. Different cell/substrate ratios also influenced the optical purity of remaining substrate. An additional stability test of the whole-cell enzyme suggests that rapid deactivation of the epoxide hydrolase was the potential reason. (R)-Epoxides were prepared in gram amounts with optical purity of 87% - 99% ee.

Catalysis↗
PubMed2004

Evaluation of plasmid DNA removal from lentiviral vectors by benzonase treatment.

To improve the purity of lentiviral vector supernatants for clinical studies we have evaluated plasmid DNA removal from lentiviral vectors and also the extent of plasmid DNA associated with transduced CD34 cells in an ex vivo transduction protocol. Optimal conditions of plasmid DNA removal by benzonase treatment were established by varying the temperature, time, and benzonase concentrations in the reaction mix and were determined to be 50 units of benzonase per milliliter of vector supernatant at 37 degrees C, for 15 min. No plasmid DNA was detected, suggesting efficient plasmid degradation was achieved under these experimental conditions. The infectious titer of benzonase-treated lentiviral vector (RRL-CMV-GFP) was nearly identical to the titer of untreated vector (2.3 +/- 0.3 x 10(6) transduction units per milliliter (TU/ml) and 2.7 +/- 0.3 x 10(6) TU/ml, respectively). Analysis of plasmid DNA in concentrated lentiviral vectors shows that concentration substantially decreases the amount of DNA per TU. Analysis of the extent of plasmid DNA associated with transduced CD34 cells in an ex vivo transduction protocol suggests that a minimal amount of plasmid is transferred to transduced cells if the vector supernatant was not previously treated with benzonase. In conclusion, benzonase treatment is effective in eliminating plasmid DNA from vector supernatants and treatment does not affect infectious titers. However, because there is minimal transfer of plasmid DNA to transduced cells under ex vivo transduction conditions, DNA removal from lentiviral vectors may not be essential for all ex vivo clinical applications.

Adult↗
PubMed2004

A family of putative MSCRAMMs from Enterococcus faecalis.

The recently published Enterococcus faecalis genome [Paulsen, I. T., Banerjei, L., Myers, G. S. & 29 other authors (2003). Science 299, 2071-2074)] was examined and 41 putative cell-wall-anchored proteins were identified. Seventeen of these proteins are predicted to contain tandemly repeated immunoglobulin-like folds characteristic of the structural organization of staphylococcal adhesins of the MSCRAMM (microbial surface component recognizing adhesive matrix molecules) type. Two of the nine proteins selected for further study appear to represent cell-wall-anchored enzymes. It is proposed that the remaining seven proteins constitute a family of structurally related proteins potentially interacting with proteins of the host. This family includes the previously identified collagen/laminin-binding MSCRAMM ACE [Rich, R. L., Kreikemeyer, B., Owens, R. T., LaBrenz, S., Narayana, S. V., Weinstock, G. M., Murray, B. E. & Hook, M. (1999). J Biol Chem 274, 26939-26945]. It is further demonstrated that genes encoding the seven putative MSCRAMMs are present in all E. faecalis strains tested and these proteins appear to be expressed during infection in humans, since sera from infected individuals contain antibodies reacting with recombinant versions of the enterococcal proteins.

Adhesins, Bacterial↗
PubMed2004

Compensation for pitch-shifted auditory feedback during the production of Mandarin tone sequences.

Recent research has found that while speaking, subjects react to perturbations in pitch of voice auditory feedback by changing their voice fundamental frequency (F0) to compensate for the perceived pitch-shift. The long response latencies (150-200 ms) suggest they may be too slow to assist in on-line control of the local pitch contour patterns associated with lexical tones on a syllable-to-syllable basis. In the present study, we introduced pitch-shifted auditory feedback to native speakers of Mandarin Chinese while they produced disyllabic sequences /ma ma/ with different tonal combinations at a natural speaking rate. Voice F0 response latencies (100-150 ms) to the pitch perturbations were shorter than syllable durations reported elsewhere. Response magnitudes increased from 50 cents during static tone to 85 cents during dynamic tone productions. Response latencies and peak times decreased in phrases involving a dynamic change in F0. The larger response magnitudes and shorter latency and peak times in tasks requiring accurate, dynamic control of F0, indicate this automatic system for regulation of voice F0 may be task-dependent. These findings suggest that auditory feedback may be used to help regulate voice F0 during production of bi-tonal Mandarin phrases.

Adult↗
PubMed2004

Clinical and microbiological effects of topical subgingival application of hyaluronic acid gel adjunctive to scaling and root planing in the treatment of chronic periodontitis.

BACKGROUND: Hyaluronic acid (HA) has shown anti-inflammatory effects in gingivitis therapy. The potential benefits of local subgingival application of HA adjunctive to scaling and root planing (SRP) were evaluated in this study. METHODS: Twenty patients with chronic periodontitis were included in this split-mouth study. Sulcus fluid flow rate (SFFR) and sulcus bleeding index were monitored at baseline and after 1, 2, 3, 4, 5, 6, and 12 weeks; probing depth and clinical attachment level were monitored at baseline and 6 and 12 weeks. Subgingival plaque samples were also taken at these same three appointments to determine the presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, and Treponema denticola. All patients were treated with full-mouth scaling and root planing (SRP); in addition, an HA gel was administered subgingivally in the test sites every week for 6 weeks. RESULTS: An improvement of all clinical variables was observed (P < 0.05) in both groups. Clinically, no difference between test and control sites could be found. No difference between test and control sites was seen in the tested microorganisms. CONCLUSIONS: No clinical or microbiological improvement was achieved by the adjunctive use of HA gel compared to SRP alone. Only SFFR was affected by the use of HA in terms of a more rapid reduction of SFFR in the test sites.

Administration, Topical↗
PubMed2004

Effect of cyclodextrin on the activity and secondary structure of horseradish peroxidase.

The activity and secondary structure of horseradish peroxidase (HRP) was studied in aqueous solution containing alpha-, beta- and gamma-cyclodextrin (CD). The results showed that the activity of HRP was enhanced to different extents by the three kinds of CD. A Fourier Transform infrared (FTIR) spectroscopy study indicated that the amount of alpha-helical structure was important for the activity of HRP. This phenomenon is discussed.

Circular Dichroism↗
PubMed2004

[Effects of Shendan Jianyi Capsule on aldose reductase activity of kidney in diabetic rats].

OBJECTIVE: To evaluate the effects of Shendan Jianyi Capsule (SDJYC) on aldose reductase (AR) activity of the kidney in diabetic rats and the significance of prevention and treatment of diabetic nephropathy with Chinese natural herbs. METHODS: Diabetic Wistar rats were treated with SDJYC and sorbinil respectively, and the AR activity in kidney, urine protein and the activity of Na(+)-K(+)-ATPase were tested. RESULTS: The AR activity in diabetic rats was decreased obviously after being treated with sorbinil or SDJYC. The activity of Na(+)-K(+)-ATPase in diabetic rats decreased obviously at the end of the eighth week, and increased after being treated with sorbinil and SDJYC. There was no difference between two treated groups after the treatment. It demonstrated that the inhibition of AR activity could improve the activity of Na(+)-K(+)-ATPase and SDJYC had the same effect. CONCLUSIONS: SDJYC exerts effects by inhibiting the activity of AR.

Aldehyde Reductase↗
PubMed2004

[Clinical study on idiopathic thrombocytopenic purpura treated with Shengxueling Granule].

OBJECTIVE: To observe the clinical effect of Shengxueling Granule (SXLG) in treating idiopathic thrombocytopenic purpura (ITP), and to study its possible mechanism. METHODS: Eighty-six cases of ITP were divided into two groups randomly. Fifty-six cases in the treatment group were treated with SXLG, a traditional Chinese medicine, and 30 cases administered with Western medicine (prednisone) were taken as control. Patients in each group took drugs for three months and were under follow-up observation. RESULTS: In SXLG-treated group, the total effective rate in 3 months was 85.71%, similar to 83.33% in prednisone-treated group (P>0.05), while the total effective rate in 6 months in the SXLG-treated group was 91.07%, higher than 53.33% of the prednisone-treated group (P<0.01), and no obvious side-effects were observed. The patients' bleeding was alleviated or stopped, and their general condition was improved. And the blood platelet count (BPC) was increased, the platelet associated immunoglobulin (PAIg) and interleukin-4 (IL-4) were markedly dropped, the level of natural killer cells activity (NKCA) increased, and the rate of T lymphocyte subsets gradually returned to normal level. Megakaryocytes tended toward maturation on bone marrow smear after SXLG treatment. All differences above were statistically significant. CONCLUSION: SXLG is an effective and safe medicine for ITP. It can regulate the cellular immunity, inhibit the platelet antibody to reduce the destruction of the platelet and to increase the number of platelet, promote the differentiation and maturation of megakaryocyte, facilitate the production and release of platelet, lower the fragility of capillary, and prevent the hemorrhagic tendency.

Adolescent↗
PubMed2004

Combined stent and coil in endovascular treatment of intracranial wide-necked and fusiform aneurysms.

BACKGROUND: Wide-necked and fusiform aneurysms are challenges for interventional neuroradiologists and neurosurgeons since they may involve entire vessels or be irregular in shape, making is possible for Guglielmi detachable coil to protrude into the parent arteries. This study was to evaluate the endovascular treatment of intracranial wide-necked and fusiform aneurysms by using a combination of stents and coils. METHODS: From October 2000 to July 2001, eighteen patients with intracranial wide-necked or fusiform aneurysms were treated with intraluminal stenting in combination with endosaccular coiling. RESULTS: Stent placement and coil packing were technically successful in all patients. There were no complications related to the procedure except for the migration of the stent in four cases. The aneurysms were embolized with the coils after precise stenting, and total occlusion was obtained in 13 cases, neck remnants in 3, and loose occlusion in 2. All the patients recovered well. Short-term follow-up angiograms suggested patency of the parent arteries without recanalization. CONCLUSIONS: A combination of endovascular stenting and coil packing may be a favorable alternative for the treatment of intracranial aneurysms that are unsuitable for surgical clipping or coil embolization. Further study is necessary to assess the long-term outcome.

Adult↗
PubMed2004

[Clinical study of hyaluronic acid in the treatment of chronic periodontitis].

OBJECTIVE: Clinical effects in local application of hyaluronic acid (HA) adjunctive to scaling and root planing (SRP) were evaluated. METHODS: In this cross over design study 20 patients with chronic periodontitis were included. Plaque index, sulcus-fluid-flow-rate (SFFR), sulcus bleeding index, probing pocket depth and attachment level were monitored. All patients were treated with full mouth SRP, in addition a HA gel was administered subgingivally in the test site every week for 6 weeks. RESULTS: A statistically significant improvement of all clinical test parameters was observed in both groups (P < 0.05). Clinically, no significant difference between test and control group could be found. However, the SFFR decreased significantly faster in the test group. CONCLUSION: No post-inflammatory tissue regeneration could be achieved by the adjunctive use of HA gel to SRP in the patients with chronic periodontitis. Due to SFFR a control of local inflammation can be achieved quickly.

Adult↗
PubMed2004

Interaction of PACls with sulfate.

This article discusses the influential factors on Al13 separation considering the interaction of sulfate with various polyaluminum chloride (PACl). The experimental results showed that the basicity (B = [OH/[Al]), the concentration of PACl and Al/SO4 ratio exhibited significant roles in the PACl-sulfate reaction. It indicated that different species in various PACl underwent different reaction pathway with sulfate. The Alc, colloidal species, formed precipitation quickly with sulfate, while Alb, oligomers and polymers, underwent slow crystallization. And Ala, monomers, reacted with sulfate to form soluble complexes. The kinetic difference of reaction made it possible to realize the separation of Alb and further purification. The decrease of Ala resulted in the limit of ferron method was also mentioned.

Aluminum Hydroxide↗
PubMed2004

Coagulation of micro-polluted Pearl River water with IPF-PACls.

Water samples collected from early March 2001 to the end of April 2002 at the branch of Pearl River around the Guangzhou City were analyzed for its micro-polluted characteristics. The coagulation behavior of polyaluminum chlorides (PACls) was then examined focusing on the effect of primary water quality and speciation distribution. The results showed that PACls exhibit better coagulation efficiency than alum in accordance with the different speciation. The turbidity removal property of PACls is evidently better than alum at low dosage. While in neutral zone (about 6.5-7.5), the turbidity removal of PACls decreases owing to the restabilization of particles at higher dosage. The organic matters in raw water exhibit marked influence on coagulation. In acidic zone, organic matters complex with polymer species and promote the formation of flocs. With an increase in pH, the complexation of organics with polymer species gradually decreases, and the removal of organics mainly depends on adsorption. The effect is evidently improved with the raise of B value.

Adsorption↗