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Biomedical subjects

X B Yang

Publications and source records attributed to X B Yang.

18 recordsLinked to original sources
PubMed2006

The effect of anisotropic architecture on cell and tissue infiltration into tissue engineering scaffolds.

A common phenomenon in tissue engineering is rapid tissue formation on the outer edge of the scaffold which restricts cell penetration and nutrient exchange to the scaffold centre, resulting in a necrotic core. To address this problem, we generated scaffolds with both random and anisotropic open porous architectures to enhance cell and subsequent tissue infiltration throughout the scaffold for applications in bone and cartilage engineering. Hydroxyapatite (HA) and poly(D,L-lactic acid) (P(DL)LA) scaffolds with random open porosity were manufactured, using modified slip-casting and by supercritical fluid processing respectively, and subsequently characterised. An array of porous aligned channels (400 microm) was incorporated into both scaffold types and cell (human osteoblast sarcoma, for HA scaffolds; ovine meniscal fibrochondrocytes, for P(DL)LA scaffolds) and tissue infiltration into these modified scaffolds was assessed in vitro (cell penetration) and in vivo (tissue infiltration; HA scaffolds only). Scaffolds were shown to have an extensive random, open porous structure with an average porosity of 85%. Enhanced cell and tissue penetration was observed both in vitro and in vivo demonstrating that scaffold design alone can influence cell and tissue infiltration into the centre of tissue engineering scaffolds.

Animals↗
PubMed2005

Sulfation of a polysaccharide produced by a marine filamentous fungus Phoma herbarum YS4108 alters its antioxidant properties in vitro.

Free radicals and other reactive oxygen species (ROS) are generated by all aerobic cells and are widely believed to play a significant role in aging as well as a number of degenerative or pathological diseases. This study compared the free radical-scavenging properties and antioxidant activity of YCP, a polysaccharide from the mycelium of a marine filamentous fungus Phoma herbarum YS 4108 and its two chemically sulfated derivatives YCP-S1 and YCP-S2. Sulfation, which masks hydroxyl groups of YCP polysaccharide molecule, could introduce new antioxidant activity, such as superoxide and hydroxyl radicals scavenging activity, metal chelating action, lipid peroxidation and linoleic acid oxidation inhibition capability. Furthermore, sulfated YCP was more potent than YCP at protecting erythrocytes against oxidative damage hemolysis. The current data suggest for the first time that sulfation of polysaccharide significantly increases its antioxidant activity and the chemical modification of polysaccharides may allow the preparation of derivatives with new properties and a variety of applications.

Animals↗
PubMed2005

Purification, characterization and enzymatic degradation of YCP, a polysaccharide from marine filamentous fungus Phoma herbarum YS4108.

YCP, a mitogenic polysaccharide with its molecular weight (MW) of 2.4 x 10(3) kDa, was isolated from the mycelium of the marine filamentous fungus Phoma herbarum YS4108 by a combination of ion-exchange chromatography on DEAE-32 and gel permeation over Sephacryl S-400. The detailed compositional, spectroscopic and methylation analyses of the polysaccharide demonstrated that its backbone possessed most likely a linear alpha-(1 --> 4) bonded glucopyranoside main chain co-bearing through side alpha-(1 --> 6)-linkage. The alpha-(1 --> 4) bondage of the glucopyranoside building blocks in YCP was confirmed by the observation that it could be hydrolyzed by the alpha-amylase produced by Bacillus licheniformis. A reliable concentration monitoring experimentation highlighted that the reducing sugars released continuously from YCP during its incubation with the enzyme, and the MW of the main resulting fragment weighed 0.8 x 10(4) Da with approximately 10% of YCP converted to maltose, maltotriose and glucose after a 120-min enzymatic degradation. Finally, YCP was found to be able to increase phagocytic activity of mice in vitro and in vivo, indicating that it may be looked up as a potent immunomodulator that could activate macrophages.

Animals↗
PubMed2003

Novel osteoinductive biomimetic scaffolds stimulate human osteoprogenitor activity--implications for skeletal repair.

The development of new bone formation strategies offers tremendous therapeutic implications in a variety of musculoskeletal diseases. One approach involves harnessing the regenerative capacity of osteoprogenitor bone cells in combination with biomimetic scaffolds generated from appropriate scaffold matrices and osteoinductive factors. The aims of our study were to test the efficacy of two innovative osteoinductive agents: the osteoblast stimulating factor-1 (osf-1), an extracellular matrix-associated protein, and osteoinductive extracts of Saos-2 cells on human osteoprogenitor cells. Saos-2 extracted osteoinductive factors significantly stimulated alkaline phosphatase specific activity in basal and osteogenic conditions. Osf-1 significantly stimulated chemotaxis, total colony formation, alkaline phosphatase-positive colony formation, and alkaline phosphatase specific activity at concentrations as low as 10 pg/ml compared with control cultures. Osteoinductive factors present in Saos-2 cell extracts and osf-1 promoted adhesion, migration, expansion, and differentiation of human osteoprogenitor cells on 3-D scaffolds. The successful generation of 3-D biomimetic structures incorporating osf-1 or osteoinductive factors from Saos-2 cells indicates their potential for de novo bone formation that exploits cell-matrix interactions.

Aged↗
PubMed2001

Anomalous origin of the pulmonary artery from the right coronary artery.

A 5-year-old boy who had an anomalous origin of a stenotic pulmonary artery from the right coronary artery with ventricular septal defect and pulmonary atresia is reported. The diagnosis was made at operation. Successful repair was achieved for the complex anomaly by using a pulmonary artery homograft as a conduit and closing the ventricular septal defect.

Blood Vessel Prosthesis Implantation↗
PubMed2001

Human osteoprogenitor growth and differentiation on synthetic biodegradable structures after surface modification.

The ability to generate new bone for skeletal use is a major clinical need. Biomimetic scaffolds that interact and promote osteoblast differentiation and osteogenesis offer a promising approach to the generation of skeletal tissue to resolve this major health-care issue. In this study we examine the ability of surface-modified poly(lactic acid) (PLA) films and poly(lactic-co-/glycolic acid) (PLGA) (75:25) porous structures to promote human osteoprogenitor adhesion, spreading, growth, and differentiation. Cell spreading and adhesion were examined using Cell Tracker green fluorescence and confocal microscopy. Osteogenic differentiation was confirmed with alkaline phosphatase activity as well as immunocytochemistry for type I collagen, core binding factor-1 (Cbfa-1), and osteocalcin. Poor cell growth was observed on nonmodified PLA films and PLGA scaffolds. The polymers were then coupled with RGD peptides [using poly(L-lysine), or PLL] and physical adsorption as well as PLA films presenting adsorbed fibronectin (FN). Both modifications enhanced cell attachment and spreading. On PLA-FN and PLA-PLL-GRGDS films, the osteoblast response was dose dependent (20 pmol/L to 0.2 micromol/L FN and 30 nmol/L to 30 micromol/L PLL-GRGDS) and significant at concentrations as low as 2 nmol/L FN and 30 nmol/L PLL-GRGDS. With optimal concentrations of FN or RGD, adhesion and cell spreading were comparable to tissue culture plastic serum controls. In PLGA (75:25) biodegradable porous scaffolds, coated with FN, PLL-GRGDS, or fetal calf serum for 24 h in alpha MEM alone, prior to growth in dexamethasone and ascorbate-2-phosphate for 4-6 weeks, extensive osteoblast impregnation was observed by confocal and fluorescence microscopy. Cell viability in extended culture was maintained as analyzed by expression of Cell Tracker green and negligible ethidium homodimer-1 (a marker of cell necrosis) staining. Alkaline phosphatase activity, type I collagen, Cbfa-1, and osteocalcin expression were observed by immunocytochemistry. Mineralization of collagenous matrix took place after 4 weeks, which confirmed the expression of the mature osteogenic phenotype. These observations demonstrate successful adhesion and growth of human osteoprogenitors on protein- and peptide-coupled polymer films as well as migration, expansion, and differentiation on three-dimensional biodegradable PLGA scaffolds. The use of peptides/proteins and three-dimensional structures that provide positional and environmental information indicate the potential for biomimetic structures coupled with appropriate factors in the development of protocols for de novo bone formation.

Aged↗
PubMed2000

Dynamic behaviors of the Ricker population model under a set of randomized perturbations.

We studied the dynamics of the Ricker population model under perturbations by the discrete random variable epsilon which follows distribution P¿epsilon=a(i)¿=p(i),i=1,ellipsis,n,0 /=1. Under the perturbations, n+1 blurred orbits appeared in the bifurcation diagram. Each of the n+1 blurred orbits consisted of n sub-orbits. The asymptotes of the n sub-orbits in one of the n+1 blurred orbits were N(t)=a(i) for i=1,ellipsis,n. For other n blurred orbits, the asymptotes of the n sub-orbits were N(t)=a(i)exp[r(1-a(i))]+a(j),j=1,2,ellipsis,n, for i=1,ellipsis,n, respectively. The effects of variances of the random variable epsilon on the bifurcation diagrams were examined. As the variance value increased, the bifurcation diagram became more blurred. Perturbation effects of the approximate continuous uniform random variable and random error were compared. The effects of the two perturbations on dynamics of the Ricker model were similar, but with differences. Under different perturbations, the attracting equilibrium points and two-cycle periods in the Ricker model were relatively stable. However, some dynamic properties, such as the periodic windows and the n-cycle periods (4), could not be observed even when the variance of a perturbation variable was very small. The process of reversal of the period-doubling, an important feature of the Ricker and other population models observed under constant perturbations, was relatively unstable under random perturbations.

Animals↗
PubMed2000

The donor foot in free toe or joint transfers.

Eighty-four cases of free second toe, multiple toe or second metatarsophalangeal joint transfers were studied by case review and follow-up. The function of the donor foot had recovered completely within 6 months in 89% of patients. The wounds on the donor foot healed in 2-3 weeks in 90% of patients. Slight numbness on the dorsal aspect of the donor foot, intolerance to cold, mild reduction in push-off, scar tenderness and pain or swelling occurred in only a few patients and generally were not considered of significance. Multiple toe transfers created more donor problems in terms of healing and appearance. Some foot deformities with plantar callosities were observed at long term review. However, all patients were capable of work and normal activities.

Adult↗
PubMed2000

Antidiabetic effect of Oenanthe javanica flavone.

AIM: To study the antidiabetic effect of Oenanthe javanica flavone (OjF). METHODS: Mice were injected i.v. with alloxan 90 mg.kg-1 to induce diabetes. Blood glucose, serum lipid, and pancreatic amylase were determined with Automatic Biochemistry Analysor. Serum insulin was determined by radioimmunoassay. The pancreas and islets were examined under microscope. RESULTS: OjF 200 mg.kg-1 reduced the blood glucose in normal mice from 0.5 to 6 h after a single administration ig. OjF 200 and 400 mg.kg-1 ig daily for 10 d decreased the blood glucose in alloxan-induced hyperglycemic mice (P < 0.05, P < 0.01). OjF promoted the release of insulin both in normal and in diabetic mice. OjF decreased serum triglyceride and raised the lowered pancreatic amylases in diabetic mice (P < 0.01, P < 0.01). The islet-injured changes of OjF-treated group were similar to those of control in histology examination, but to a lesser degree. CONCLUSION: OjF possessed the hypoglycemic and hypotriglyceride actions, mainly concerned with promoting release of insulin from B-cells in islets of langerhans.

Amylases↗
PubMed1997

Long-term results of toe transfer: retrospective analysis.

Between February 1966 and February 1994, 400 cases of toe transplantation were analyzed, to evaluate toe-transfer procedures in thumb and finger reconstruction. Techniques utilized included single second-toe transfer, with and without the metatarsophalangeal joint (299): second- and third-toe transfer (28); second-toe and third proximal phalanx transfer (1); second-toe with flap transfers (66); and hallux nail flap with second toe or second and third toe transfer (6). There was a survival rate of 96.5 percent, with 386 cases surviving and 14 failing. A more than 2-year follow-up was possible in 240 cases. Excellent motor and sensory function (more than 90 percent of normal) was achieved in the reconstructed fingers and thumbs, as well as satisfactory function (between 86 and 91 percent of normal) in the donor foot.

Adolescent↗
PubMed1997

[Two new flavanone glycosides from Glycyrrhizia inflata].

Two new flavanone glycosides having two chains of sugar moeity were isolated from the roots of Glycyrrhizia inflata Bat by repeated CC and HPLC. They were identified to be liquiritigenin-7-O-beta-D-apiofuranosyl-4'-O-beta-D-glucopyranoside(I) and liquiritigenin-7-O-beta-D-(3-O-acetyl)-apiofuranosyl-4'-O-beta-D- glucopyranoside (II) on the basis of chemical and spectroscopic methods.

Drugs, Chinese Herbal↗
PubMed1996

[(Sp)-8-chloroadenosine 3',5'-cyclophosphate induced differentiation on human leukemia HL-60 cells].

(Sp)-octyl 8-chloroadenosine 3',5'-cyclophosphate(OCC), a newly synthesized cAMP analog, strongly induced growth inhibition and differentiation in human leukemia HL-60 cells. The effects were dose- and time-dependent and irreversible. In flow cytometry, OCC brought about a block at the G1 phase of HL-60 cell cycle. Determined by incorporation assay, OCC was shown to strongly inhibit DNA synthesis without affecting the synthesis of RNA and protein in HL-60 cells. OCC activated the protein kinase A(PKA) in the cytosol of HL-60 cells and inhibited its binding to cAMP. The activities of PKA in the cytosol of HL-60 cells treated with OCC were more significantly increased than those in control cells. It can be concluded that OCC binds itself to PKA in competition with cAMP and, as a result, activates PKA.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMedDate not supplied

Nucleophilic N1-->N3 rearrangement of 5'-O-trityl-O2,3'-cycloanhydrothymidine.

5'-O-Trityl-O2,3'-cycloanhydrothymidine (1) heated at 150 degrees C in the presence of O,O-diethyl phosphate or O,O-diethyl phosphorothioate anions undergoes rearrangement into N3-isomer (2); its structure was established by both advanced NMR methods and X-ray crystallographic studies. The most probable mechanism of 1-->2 rearrangement relies upon reversibility of glycosidic bond cleavage process.

Crystallography, X-Ray↗