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Biomedical subjects

Y Shi

Publications and source records attributed to Y Shi.

At least 127 records · Page 7Linked to original sources
PubMed2001

Fast repair of the radical cations of dCMP and poly C by quercetin and rutin.

The effects of quercetin and rutin on the repair of the radical cations of dCMP and poly C were studied using the technique of pulse radiolysis. The radical cations of dCMP and poly C were formed by the reaction of dCMP and poly C with SO( 4)(-). After pulse irradiation of nitrogen-saturated aqueous solutions containing dCMP, 20 mM K(2)S(2)O(8), 200 mM t-BuOH and either rutin or quercetin, the initially formed radical cation of dCMP, detected spectrophotometrically, rapidly decayed with the concurrent formation of the phenoxyl radical of rutin or quercetin within 8-40 micros. The repair efficiencies of the tested compounds towards the poly C radical cation were also determined using the same procedure. The results indicate that dCMP and poly C radical cations can be rapidly repaired by quercetin and rutin. The rate constants of the repair reactions were determined to be 4.3-8.8x10(8) M/s and 1.5-3.6x10(8) M/s for dCMP and poly C radical cations, respectively. Together with findings from our previous studies, the present results demonstrate that non-enzymatic fast repair may be a universal form of repair involving phenolic antioxidants.

Antioxidants↗
PubMed2001

Tissue-engineered bone repair of sheep cranial defects with autologous bone marrow stromal cells.

Cranial bone defect remains a major challenge to craniofacial surgeons because of limited availability of autologous bone graft to repair the defects and the donor site defects secondary to tissue harvesting. In contrast, tissue-engineering technique can generate a large bone tissue using small amount of autologous cells and therefore avoid these problems. Bone Marrow Stromal Cells (MSCs) have the potential of multi-lineage (including osteogenic) differentiation. The objective of this study was to investigate the potential of using autologous MSCs to repair cranial bone defects by a tissue-engineering approach. Autologous MSCs were isolated from eight adult sheep respectively and were in vitro expanded and induced to become osteogenic cells. Bilateral full-thickness defects (20 mm in diameter) of parietal bones were created in animals and the bone defects were either repaired with the bone implants constituted with MSCs and calcium alginate at the experimental side (n = 8) or treated with calcium alginate only without MSCs (n = 4) or left unrepaired (n = 4) at the control side. New bone tissues were observed either grossly or histologically at the defects of experimental group as early as 6 weeks post-repairing, but not in control groups. The engineered bone tissue became more mature at 18 weeks post-repairing. Three-dimensional computerized tomography (CT) scan revealed an almost complete repair of the defect of experimental group at 18 weeks. This study may provide insight for future clinical repair of cranial defect.

Alginates↗
PubMed2001

Adenosine A1 receptor antagonist prolongs survival in the hypoxic rat.

The hypothesis that adenosine A1 receptor (A1AdoR) selective antagonism limits cardiac depression and prolongs survival during acute global hypoxia was tested in a postinsult treatment model using KW-3902 ([8-(noradamantan-3-yl)-1,3-dipropylxanthine]), an A1AdoR selective antagonist. Rats were anesthetized, paralyzed, then ventilated with 8% O2 (hypoxia). In protocol I, 5 min after hypoxia, rats were treated with saline, drug vehicle, or KW-3902 (0.1 mg/kg i.v.). In protocol II, KW-3902 treatment occurred 2.5, 5, or 7.5 min after hypoxia. In protocol I, after hypoxia, left ventricular contractility, heart rate, and systemic mean arterial blood pressure decreased rapidly in saline-and vehicle-treated groups. In contrast, KW-3902 significantly attenuated the decline in these variables. Survival time (the time from the commencement of hypoxia until death) was more prolonged with KW-3902 (109.5 +/- 9.1 min) than with saline (37.6 +/- 5.0 min) or vehicle (35.0 +/- 4.2 min) (p < 0.001). In protocol II, survival time increased from 29.2 +/- 5.5 min in the 7.5-min treatment group to 109.5 +/- 9.5 min (5-min group) and 245.9 +/- 26.1 min (2.5-min group; p < 0.001). KW-3902 prolongs survival in this model, presumably by antagonizing A1AdoR-mediated inhibition of cardiac function. Also, treatment efficacy is highly time dependent.

Analysis of Variance↗
PubMed2001

Nocardia beijingensis sp. nov., a novel isolate from soil.

The taxonomic status of a soil isolate, provisionally assigned to the genus Nocardia, was established following a polyphasic study. An almost complete sequence of the 16S rDNA of the strain was determined and aligned with available sequences for nocardiae and phylogenetic trees were inferred using four tree-making algorithms. The organism was associated consistently with the type strains of Nocardia brasiliensis and Nocardia farcinica in the neighbour-joining analysis, albeit with low bootstrap values. It was also found to have chemotaxonomic and morphological properties consistent with its assignment to the genus Nocardia. The organism was readily separated from representatives of other Nocardia species by a broad range of phenotypic properties. The name proposed for the novel species is Nocardia beijingensis sp. nov. The type strain is AS4.1521T (= IFO 16342T = JCM 10666T).

Base Composition↗
PubMed2001

Synthetic phase tuning of guided waves.

A novel method has been developed to generate and manipulate multi-mode guided waves. This technique uses a linear phased array whose elements are activated according to a prescribed time delay profile obtained from the dispersion curves. It is shown that a desired guided wave mode can be tuned by synthetically constructing a virtual wave from individually acquired waveform data. In addition to the development of such a synthetic phase tuning (SPT) technique, a pseudo pulse-echo (PPE) operation scheme is also developed for nondestructive testing. Experimental results are compared with those obtained by more traditional techniques using variable angle wedges and array transducers. It was shown that the new technique is convenient, robust, and flexible in utilizing multi-mode guided waves for nondestructive evaluation (NDE). It is a dynamic method that can produce desired guided wave modes propagating in the desired direction without any mechanical alignment. The advantages and limitations of the technique are addressed.

Journal Article↗
PubMed2001

Selection and characterization of varicella-zoster virus variants resistant to (R)-9-[4-hydroxy-2-(hydroxymethy)butyl]guanine.

(R)-9-[4-Hydroxy-2-(hydroxymethy)butyl]guanine (H2G) is a potent and selective inhibitor of herpesvirus replication. It is a nucleoside analog, and its triphosphate derivative (H2G-TP) is a competitive inhibitor of herpesvirus DNA polymerases. In this study, the antiviral activities of H2G and acyclovir (ACV) and the development of viral resistance to these agents were compared in varicella-zoster virus (VZV)-infected cells. In plaque reduction assays, the 50% effective concentration of H2G for VZV was 60- to 400-fold lower than that of ACV, depending on the virus strain and the cell line tested. The enhanced efficacy of H2G against VZV can be accounted for in part by the fact that the intaracellular H2G-TP level (>170 pmol/10(6) cells) is higher than the intracellular ACV-TP level (<1 pmol/10(6) cells). In addition, H2G-TP has extended half-lives of 3.9 and 8.6 h in VZV-infected MRC-5 and MeWo cells, respectively. To assess the emergence of H2G-resistant VZV in vitro, VZV was passaged in the presence of increasing concentrations of H2G. Earlier in the passage, when the concentration of H2G was relatively low, the predominant variant had the (A)76 deletion in the viral thymidine kinase (TK) gene. This mutant was identical to an ACV-resistant mutant generated in parallel experiments. However, higher concentrations of H2G appeared to favor a novel mutant, which had deletions of two consecutive nucleotides at positions 805 and 806 of the TK gene. All of these changes introduced frameshift mutations in the TK gene resulting in the expression of truncated polypeptides. H2G-resistant viruses were cross-resistant to ACV, and vice versa.

Acyclovir↗
PubMed2001

Comparison of precancerous conditions: atrophy and intestinal metaplasia in Helicobacter pylori gastritis among Chinese and Dutch patients.

AIM-Atrophy and intestinal metaplasia (IM) as precancerous conditions consistently begin in the antrum and are most severe along the lesser curvature. The aim of this study was to investigate discrepancies in the prevalence, the severity of atrophy, and IM in antral mucosa of Helicobacter pylori infected gastritis and difference in age of onset among Chinese and Dutch patients. METHODS-Two hundred and sixty five Chinese patients and 261 Dutch patients with H pylori infection were enrolled. The degrees of atrophy and IM were graded according to the updated Sydney system. RESULTS-The overall prevalences of atrophy and IM were lower in Dutch patients (42% and 26%, respectively) than in Chinese patients (52% and 32%, respectively). Only the difference in atrophy reached significance (p = 0.028). However, in both Chinese and Dutch patients, the degrees of atrophy and IM were low and severe degrees were rare. The mean ages of Chinese and Dutch patients with atrophy and IM were higher than those without atrophy and IM (with atrophy (Chinese patients): mean, 42.12; SD, 9.80; with IM (Chinese patients): mean, 42.56; SD, 9.96; with atrophy (Dutch patients): mean, 55.16; SD, 12.20; with IM (Dutch patients): mean, 57.79; SD, 11.13; without atrophy (Chinese patients): mean, 39.71; SD, 10.16; without IM (Chinese patients): mean, 40.19; SD, 9.99; without atrophy (Dutch patients): mean, 45.70; SD, 12.44; without IM (Dutch patients): mean, 46.89; SD, 12.68). Atrophy and IM occurred earlier and were more severe in Chinese patients, with both reaching a peak value in patients over 60 years. CONCLUSIONS-There are geographical differences in the prevalence and severity of H pylori infected gastritis, in particular with respect to atrophy and IM, which suggests that infection with H pylori occurs earlier in life and has a higher prevalence in CHINA:

Adolescent↗
PubMed2001

Increased NAD(P)H oxidase and reactive oxygen species in coronary arteries after balloon injury.

Reactive oxygen species (ROS), produced by cellular constituents of the arterial wall, provide a signaling mechanism involved in vascular remodeling. Because adventitial fibroblasts are actively involved in coronary remodeling, we examined whether the changes in the redox state affect their phenotypic characteristics. To this end, superoxide anion production and NAD(P)H oxidase activity were measured in porcine coronary arteries in vivo, and the effect of ROS generation on adventitial fibroblast proliferation was examined in vitro. Superoxide production (SOD- and Tiron-inhibitable nitro blue tetrazolium [NBT] reduction) increased significantly within 24 hours after balloon-induced injury, with the product of NBT reduction present predominantly in adventitial fibroblasts. These changes were NAD(P)H oxidase-dependent, because diphenyleneiodonium (DPI) abolished superoxide generation (P<0.001). Furthermore, the injury-induced superoxide production was associated with augmented NAD(P)H oxidase activity and upregulation of p47(phox) and p67(phox) in adventitial fibroblasts (immunohistochemistry). Serum stimulation of isolated adventitial fibroblasts produced time-dependent increases in ROS production (peak 3 to 6 hours). The inhibition of ROS generation with NAD(P)H oxidase inhibitor (DPI) or the removal of ROS with antioxidants (Tiron, catalase) abrogated proliferation of adventitial fibroblasts. These results indicate that vascular NAD(P)H oxidase plays a central role in the upregulation of oxidative stress after coronary injury, providing pivotal growth signals for coronary fibroblasts.

Animals↗
PubMed2001

Compositional effects on milk fat crystallization.

Seasonal and regional variability in milk fat composition causes differences in crystallization behavior, which can, for example, result in variability in fractionation efficiency and physical properties of butter. However, the specific compositional causes of variability in milk fat crystallization behavior are still only poorly understood. In this work, the seasonal and regional variations in composition of anhydrous milk fat were analyzed and related to crystallization behavior. Although there were no clear-cut trends in chemical composition (triacylglycerol, fatty acid, and minor lipid profiles) among the milk fats, significant differences in crystallization behavior were observed. For anhydrous milk fat samples made from sweet cream and obtained from the same milk supply through a period of 14 mo, no significant trends in either composition or crystallization behavior were observed. This suggests that seasonal variability of milk fat may be reduced by current feeding strategies in the United States. More detailed examination of the triacylglycerol profiles led to the conclusion that the relative contents of certain triacylglycerol combinations correlated well with crystallization behavior. In particular, the ratio of higher-melting to lower-melting triacylglycerols could be used to predict crystallization behavior. Higher ratios of higher-melting triacylglycerols led to higher crystallization rate.

Animals↗
PubMed2001

[Measurement of lead in high-salt food with sulfuric-nitric acid to treat food ash].

Lead in high-salt food was measured by treating the ash with sulfuric-nitric acid, and diluting lead standard with sodium sulfate to eliminate the disturbance of chloride in detecting lead with atomic absorption spectrophotometry. The minimum detection limit was 0.10 mg/kg. The relative standard deviation is 1.72%, 5.00% and 7.14% while the amount of lead was 8.70, 2.40 and 1.40 micrograms respectively. The recovery varied between 90.0%-109.0%. There was no significant difference (P > 0.05) of the lead content between the mentioned method and extraction flame photometry. The amount of lead is higher obviously than that of other two methods by eliminating the disturbance of chloride. The method was simple, precise and accurate, and suitable for hygienic examination.

Food Contamination↗
PubMed2001

[Large-capacity expanded cytoline-induced killer cells and its cytotoxic activity].

This study was conducted to establish the large-capacity culture methd of cytokine-induced killer (CIK) cells for clinical therapy and assess its effect on the fuction of cell-mediated immunity following autologous CIK cells reinfusion. Autologus CIK cells were expanded in 1000 ml culture-bag and reinfused back. The MTT method was used to test the cytotoxic activity of CIK cells before and after reinfusion. The results showed that the total amount of autologous CIK cells reinfusion exceeded 1.6 x 10(10) with the use of the culture method of large-capacity. The PBMNC from patients treated by CIK cells showed significant increase in cytotoxic activity, no side effects were observed, and therefore the large-capacity culture method of CIK cells is a simle and safe therapy for treating the minimum residue of diseases.

Adult↗
PubMed2001

[Lipopolysaccharide upregulates expression of CD14 gene and CD14 proteins of hepatocytes in rats].

OBJECTIVE: To observe the expression of CD14 mRNA and its protein in rat hepatocytes during endotoxemia. METHODS: The acute endotoxemia model of wistar rats was established by injection of a dose of LPS (5mg/kg, Escherichia coli O111:B4) via the tail vein, then the rats were sacrificed at 3, 6, 12, and 24 hour, respectively. Hepatocytes were isolated from normal and LPS-injected rats by in situ collagenase perfusion technique. Hepatocytes and hepatic tissue were collected to measure the expression of CD14 mRNA and CD14 protein by reverse transcriptase-polymerase chain reaction (RT-PCR) or Western blot analysis. The binding of fluorescein isothiocyanate (FITC)-CD14 polyclone antibody to isolated hepatocytes was also assessed by flow cytometric analysis (FCM). RESULTS: In the rats with endotoxemia, the expression of CD14 mRNA and CD14 protein in hepatic tissue and isolated hepatocytes were stronger at 6, 12 and 24 hour than that in control rats (P<0.01). FCM showed that positive cell numbers of FITC-CD14 in the rats with endotoxemia increased when compared with normal control group (P<0.01). CONCLUSIONS: LPS can markedly upregulate the expression of CD14 mRNA and CD14 proteins in hepatic tissue and isolated hepatocytes.

Animals↗
PubMed2001

[Comparison between porous polymer carrier and activated carbon carrier used for treating organic wastewater in anaerobic fluidized-bed reactor].

A comparative performance between porous polymer carriers (HP) and granular activated carbon carriers (GAC) in anaerobic fluidied-bed reactors was undertaken to evaluate their characters. The results showed that the COD removal and the biogas volume yield rate were 84% and 16.5 m3/(m3.d) respectively when HP was used as carrier to treat synthetic wastewater, at the top COD organic load rate of 65.5 kg/(m3.d), however those were 74.2% and 14.5% respectively for GAC carrier at the top load rate of 63.25 kg/(m3.d). The COD removal and biogas volume yield rate were 64.7%-54.5% and 1.89-2.7 m3/(m3.d) respectively when HP was used as carriers to treat straw pulping wastewater, at the load rate of 14.5-36.15 kg/(m3.d), and those were 61.0%-52.1% and 0.73-2.0 m3/(m3.d) respectively for GAC carriers at the load rate 9.16-19.06 kg/(m3.d). The study revealed that the HP carriers reactor is more efficient than the GAC carriers reactor in microbial immobilization and the wastewater treatment.

Anaerobiosis↗
PubMed2001

[Effect of different cultured conditions on endothelial cell and its resistance to the fluid imposed shear stress--a comparative study].

This study was intended to enhance the resistance of cultured endothelial cells (EC) to fluid shear stress and clarify the possible mechanism. A modified parallel plate flow apparatus was used to compare the strength between the grafts and the endothelial cells under shear stress condition and static condition. The dynamic change of cytoskeletal actin filaments and the effects of different adhesive proteins coated on the strength of EC adhesion to the glass were studied. The results showed that the number of cells retention of the shear stress-conditioned group was significantly larger than that of the static group. Precoated fibronectin and laminin significantly promoted the adherence of the EC cultured in a steady environment but seemed to have no effect on the EC cultured under flow condition. The results suggest that the vascular endothelial cell cytoskeleton, stress fiber and the shape of EC reorganize in response to long term fluid-imposed shear stress, and the endothelial cells become tightly adherent to the grafts.

Actins↗
PubMed2001

[Design and improvement of stenosis model in cylindrical tubal flow via pulsed Doppler ultrasound in vitro].

A model of disturbed flow downstream of a severe stenosis has been established and improved in vitro, and the relevant method and feasibility for the detection of flow indices are discussed via commercially available Pulsed Doppler Ultrasound (PDU). Detection is done temporally and spatially, upstream and downstream. The methodology is proved to be feasible and has good prosperity of clinical use.

Constriction, Pathologic↗
PubMed2001

[RGD peptides and endothelialization of biomaterials].

Endothelialization can remarkably improve blood compatibility of biomaterials and promote their clinical application, especially the uses of cardiovascular grafts. The attachment and growth of endothelial cells on artificial surfaces is the critical factor affecting the process of endothelialization. Many adhesive proteins contain the Arg-Gly-Asp(RGD) sequence which plays an important role in cell adhesion, migration and growth. In this review, the interaction of RGD peptides sequence and integrins, the influential factors of RGD peptides bioactivity and its application in endothelialization of biomaterials were discussed.

Biocompatible Materials↗
PubMed2001

Genomic in situ hybridization (GISH) discriminates between the A and the B genomes in diploid and tetraploid Setaria species.

Genomic in situ hybridization (GISH) was used to investigate genomic relationships between different Setaria species of the foxtail millet gene pool (S. italica) and one interspecific F1 hybrid. The GISH patterns obtained on the two diploid species S. viridis (genome A) and S. adhaerans (genome B), and on their F1 hybrid showed clear differentiation between these two genomes except at the nucleolar organizing regions. Similar GISH patterns allowed differentiation of S. italica from S. adhaerans. However, GISH patterns did not distinguish between the genomes of S. italica and its putative wild ancestor S. viridis. GISH was also applied to polyploid Setaria species and enabled confirmation of the assumed allotetraploid nature of S. faberii and demonstration that both S. verticillata and S. verticillata var. ambigua were also allotetraploids. All these tetraploid species contained two sets of 18 chromosomes each, one from genome A and the other from genome B. Only one polyploid species, S. pumila, was shown to bear an unknown genomic composition that is not closely related either to genome A or to genome B.

Animals↗