Biomedical subjects

Jian Yang

Publications and source records attributed to Jian Yang.

At least 127 records · Page 7Linked to original sources

PubMed2004

Biodegradable polyester elastomers in tissue engineering.

Tissue engineering often makes use of biodegradable scaffolds to guide and promote controlled cellular growth and differentiation in order to generate new tissue. There has been significant research regarding the effects of scaffold surface chemistry and degradation rate on tissue formation and the importance of these parameters is widely recognised. Nevertheless, studies describing the role of mechanical stimuli during tissue development and function suggest that the mechanical properties of the scaffold will also be important. In particular, scaffold mechanics should be taken into account if mechanical stimulation, such as cyclic strain, will be incorporated into strategies to grow improved tissues or the target tissue to be replaced has elastomeric properties. Biodegradable polyesters, such as polyglycolide, polylactide and poly(lactide-co-glycolide), although commonly used in tissue engineering, undergo plastic deformation and failure when exposed to long-term cyclic strain, limiting their use in engineering elastomeric tissues. This review will cover the latest advances in the development of biodegradable polyester elastomers for use as scaffolds to engineer tissues, such as heart valves and blood vessels.

Animals↗

PubMed2004

Leukocyte-derived myeloperoxidase amplifies high-glucose--induced endothelial dysfunction through interaction with high-glucose--stimulated, vascular non--leukocyte-derived reactive oxygen species.

Vascular non-leukocyte-derived reactive oxygen species (ROS), such as superoxide and hydrogen peroxide (H(2)O(2)), have emerged as important molecules in diabetic endothelial dysfunction. In addition, leukocyte-derived myeloperoxidase (MPO) has been implicated in vascular injury, and its injury response is H(2)O(2) dependent. It is well known that MPO can use leukocyte-derived H(2)O(2); however, it is unknown whether the vascular-bound MPO can use high-glucose-stimulated, vascular non-leukocyte-derived H(2)O(2) to induce diabetic endothelial dysfunction. In the present study, we demonstrated that MPO activity is increased in vessels from diabetic rats. In high-glucose-incubated rat aortas and in carotid arteries from rats with acute hyperglycemia, vascular-bound MPO utilized high-glucose-stimulated H(2)O(2) to amplify the ROS-induced impairment of endothelium-dependent relaxation via reduction of nitric oxide bioavailability. Hypochlorous acid (HOCL)-modified LDL, a specific biomarker for the MPO/HOCL/chlorinating species pathway, was detected in LDL- and MPO-bound vessels with high-glucose-stimulated H(2)O(2). The results suggest that vascular-bound MPO could use high-glucose-stimulated H(2)O(2) to amplify high-glucose-induced injury in the vascular wall. MPO/H(2)O(2)/HOCL/chlorinating species may represent an important pathway in diabetes complications and a new mechanism in phagocyte- and systemic infection-induced exacerbation of diabetic vascular diseases.

Animals↗

PubMed2004

Pulmonary functional MRI: an animal model study of oxygen-enhanced ventilation combined with Gd-DTPA-enhanced perfusion.

BACKGROUND: The assessment of regional pulmonary ventilation and perfusion is essential for the evaluation of a variety of lung disorders. Pulmonary ventilation MRI using inhaled oxygen as a contrast medium can be obtained with a clinical MR scanner, without additional equipment, and has been demonstrated to be a feasible means of assessing ventilation in animal models and some clinical patients. However, few studies have reported on MR ventilation-perfusion imaging. In this study, we evaluated the usefulness of oxygen-enhanced ventilation in combination with first-pass Gd-DTPA-enhanced perfusion MRI in a canine model of pulmonary embolism and airway obstruction. METHODS: Peripheral pulmonary embolisms were produced in eight dogs by intravenous injection of gelfoam strips at the pulmonary segmental arterial level, and airway obstructions were created in five of the dogs by inserting a self-designed balloon catheter into a secondary bronchus. Oxygen-enhanced MR ventilation images were produced by subtracting images from before and after inhalation of pure oxygen. Pulmonary perfusion MR images were acquired with a dynamic three-dimensional fast gradient-echo sequence. MR ventilation and perfusion images were read and contrasted with results from general examinations of pathological anatomy, ventilation-perfusion scintigraphy, and pulmonary angiography. RESULTS: Regions identified as having airway obstructions matched using both MR ventilation and perfusion imaging, but regions of pulmonary embolisms were mismatched. The area of airway obstruction defects was smaller using MR ventilation imagery than that using ventilation scintigraphy. Abnormal perfusion regions due to pulmonary embolisms were divided into defective regions and reduced regions based on the time course of signal intensity changes. In the diagnosis of pulmonary embolisms with the technique of ventilation and perfusion MRI, sensitivity and specificity were 75.0% and 98.1%, respectively, and the diagnostic results of this MRI technique were in agreement with the results of ventilation-perfusion scintigraphy and pulmonary angiography (K: 0.899, 0.743). CONCLUSIONS: Oxygen-enhanced ventilation in combination with pulmonary perfusion MRI can be used to diagnose abnormalities of airways and blood vessels in the lungs, and can provide regional functional information with high spatial and temporal resolution. This method possesses great potential value for clinical applications.

Airway Obstruction↗

PubMed2004

[An experimental study on the repair mechanism after pulmonary embolism].

OBJECTIVE: To study the role of basic fibroblast growth factor (bFGF) and small vascular density in the repair mechanism after pulmonary embolism (PE). METHODS: After peripheral pulmonary arteries had been embolized, 8 dogs were killed 1, 7, 14, and 28 days after embolization. One piece of tissue was taken from the region embolized and unembolized respectively, then HE staining and immunohistochemical staining were performed. The pathological change of the lung, changes of small vascular density and expression of bFGF were observed, and were compared between regions embolized and unembolized at different time points. RESULTS: (1) The course of pathological change during the pulmonary embolism period. (2) The bFGF was increased from 1st day to 14th day after PE (1st day: chi(2) = 44.335, 7th day: chi(2) = 71.911, 14th day: chi(2) = 84.460; P < 0.01), and decreased to normal on 28th day (chi(2) = 2.961, P > 0.05). (3) Small vascular density in embolized region (4.56 +/- 0.50) showed no statistical difference from that of unembolized region (4.11 +/- 0.76) on 1st day (P > 0.05), while it (7th day: 10.17 +/- 1.08, 14th day: 10.54 +/- 0.93, 28th day: 11.47 +/- 1.11) was significantly higher than that of unembolized region (7th day: 6.17 +/- 0.90, 14th day: 7.55 +/- 1.19, 28th day: 7.03 +/- 1.24) after embolized 7, 14, 28 days (P < 0.05). CONCLUSIONS: After PE, with increased expression of bFGF in embolized region, the formation of collateral arteries between pulmonary artery system and bronchial artery system is promoted, and absorption of the transuded blood cells and fluid is accelerated. This mechanism may be important in prevent pulmonary infarction.

Animals↗

PubMed2004

[Studies on chemical constitutents in roots of Jasminum sambac].

OBJECTIVE: To isolate and identify the chemical constitutents in roots of Jasminum sambac. METHOD: The compounds were isolated by means of chromatography and the structures were identified on the basis of physical and spectral data. RESULT: Dotriacontanoic acid, dotriacontanol, oleanolic acid, daucosterol and hesperidin were elucidated. CONCLUSION: All compounds were found in this plant for the first time.

Hesperidin↗

PubMed2004

Treatment of anthraquinone dye wastewater by hydrolytic acidification-aerobic process.

Experiment on microbial degradation with two kinds of biological process, hydrolytic acidification-aerobic process and aerobic process was conducted to treat the anthraquinone dye wastewater with COD(Cr) concentration of 400 mg/L and chroma 800. The experimental result demonstrated that the hydrolytic-aerobic process could raise the biodegradability of anthraquinone dye wastewater effectively. The effluent COD(Cr) can reach 120-170 mg/L and chroma 150 which is superior to that from simple aerobic process.

Anthraquinones↗

PubMed2003

Plasma-treated, collagen-anchored polylactone: Its cell affinity evaluation under shear or shear-free conditions.

Poly(L-lactic acid)(PLLA) and poly(L-lactic-co-glycolic acid) (PLGA) (85/15) were modified by plasma treatment. Then they were collagen anchored (PT/CA), and the cell affinity was evaluated by cell culture under shear or shear-free conditions. A convenient and "intuitionistic" dyeing method has been proposed for measuring the modified depth when plasma treatment is applied for the treatment of porous scaffolds. A parallel plate flow chamber was developed in order to study the cell affinity of a material under shear stress. Our results show that a porous scaffold can be modified by plasma treatment and that a depth of about 4.0 mm for this modification can be reached with NH(3) plasma treatment (50 w, 20 Pa, 5 min). PT/CA modification is an effective surface modification method for facilitating cell transplantation and improving the cell affinity of three-dimensional porous cell scaffolds in tissue engineering. It can solve the problem of non-uniform cell distribution in most synthetic porous cell scaffolds. Using the flow chamber system, a series of quantitative data, including cell adherent fraction, cell area, and mean shape, were compared to evaluate the cell affinity of PLLA before and after PT/CA modification. The results indicate that the quality of cell attachment on PT/CA-modified PLLA apparently is better than that on unmodified PLLA. The flow chamber system potentially may be a tool for evaluating surface modification methods.

3T3 Cells↗

PubMed2003

Identification and characterization of simple sequence repeats in the genomes of Shigella species.

A variety of simple sequence repeats (SSRs) have been identified in the genome of Shigella flexneri serotype 2a (strain Sf301), an enteric pathogen that causes bacillary dysentery in man. The distribution of SSRs, with unit length ranging from 1 to 9 nucleotides, was biased in different regions of the genome. The tri-, tetra- and hexanucleotide SSRs prevailed in the coding regions while the mono- and dinucleotide SSRs were more common in the noncoding regions. Many intergenic SSRs are less than 30 bp away from the downstream open reading frames (ORFs), suggesting a potential role in transcriptional regulation. To study polymorphism of SSRs, we compared 17 coding-region SSRs from strain Sf301 with the corresponding sequences from 23 other strains of four Shigella species. Five chromosomal loci were found to be polymorphic, of which those from S. flexneri strains were most variable. Particularly interesting is the C5-1 locus in the coding sequence of the hcaD gene encoding a subunit of ferredoxin reductase. Depending on the insertion of variable numbers of the unit sequence (CGCAG), the Shigella hcaD genes can encode truncated products due to premature stop codons or frame shifts, or products with extended core alpha helices that leads to radical alterations in the predicted tertiary structure. Hence, SSRs may serve as genotyping markers for epidemiological investigations, and may offer insights into evolutionary adaptation of the pathogens.

Amino Acid Sequence↗

PubMed2003

Metabolomics spectral formatting, alignment and conversion tools (MSFACTs).

MOTIVATION: The amplified interest in metabolic profiling has generated the need for additional tools to assist in the rapid analysis of complex data sets. RESULTS: A new program; metabolomics spectral formatting, alignment and conversion tools, (MSFACTs) is described here for the automated import, reformatting, alignment, and export of large chromatographic data sets to allow more rapid visualization and interrogation of metabolomic data. MSFACTs incorporates two tools: one for the alignment of integrated chromatographic peak lists and another for extracting information from raw chromatographic ASCII formatted data files. MSFACTs is illustrated in the processing of GC/MS metabolomic data from different tissues of the model legume plant, Medicago truncatula. The results document that various tissues such as roots, stems, and leaves from the same plant can be easily differentiated based on metabolite profiles. Further, similar types of tissues within the same plant, such as the first to eleventh internodes of stems, could also be differentiated based on metabolite profiles. AVAILABILITY: Freely available upon request for academic and non-commercial use. Commercial use is available through licensing agreement http://www.noble.org/PlantBio/MS/MSFACTs/MSFACTs.html.

Cluster Analysis↗

PubMed2003

Identification, synthesis and bioassay for the metabolites of P6A.

The metabolites Ala-Arg-Pro-Ala-OH, Ala-Arg-Pro-OH, Arg-Pro-Ala-Lys-OH and Pro-Ala-Lys-OH were identified by HPLC/ESI/MS from the in vivo blood of Ala-Arg-Pro-Ala-Lys-OH (P6A) received mice. The in vitro incubation of P6A in the blood of mice the same metabolites were also found by use of the Prep LC System. The protective intermediates of these metabolites were prepared via the solution method using the stepwise synthesis in 77.4, 90, 88, and 80% yield, respectively. After deprotection with catalytic hydrogenation the intermediates were converted into the corresponding sequences Arg-Pro-Ala-Lys-OH, Pro-Ala-Lys-OH, Ala-Arg-Pro-Ala-OH, and Ala-Arg-Pro-OH in 90, 95, 85% and 86% yield, respectively. In the thrombolysis in vivo assay the synthetic Ala-Arg-Pro-Ala-OH, and Ala-Arg-Pro-OH exhibited no activity. On the other hand the thrombolytic activity of Arg-Pro-Ala-Lys-OH was comparable to P6A, and an enhanced thrombolytic activity was observed for Pro-Ala-Lys-OH. In the in vitro fibrinolytic lysis tests the approximate results were obtained and an enhanced activity was also observed for Pro-Ala-Lys-OH. In the euglobulin clot lysis time tests P6A, Arg-Pro-Ala-Lys-OH and Pro-Ala-Lys-OH gave significantly shorter time than that given by UK, demonstrating their fast action.

Animals↗

PubMed2003

Acceleration effect of basic fibroblast growth factor on the regeneration of peripheral nerve through a 15-mm gap.

In this study, nerve guides composed of poly(D,L-lactide) (PDLLA) were fabricated and used in the repair of transected sciatic nerves (15-mm gaps) of rats. Nerve guides with a two-ply structure (inner layer dense, outer layer microporous) were prepared by controlling the solvent evaporation rate. Then basic fibroblast growth factor (bFGF) was embedded in the inner layer of the nerve guides. Thus the inner dense layer not only could prevent the ingrowth of fibroblast and avoid the outgrowing nerve cable, but it also could retain the released bFGF in the guide lumen. The outer porous layer allowed vascular ingrowth and the diffusion of essential nutrients into the guide lumen. The data show that by using this nerve guide, the transected 15-mm sciatic nerve was regenerated successfully within 4 months. The recovery of function of the regenerated nerves was significantly accelerated by bFGF, as indicated by an electrostimulation test and histologic assays. In addition, the bFGF retained its bioactivity during embedding and continuously was released from the matrix, as confirmed by the results of both the dorsal root ganglia (DRG) and the Schwann cell culture in the presence of PDLLA matrix containing bFGF. The released bFGF enhanced the ability of the nerve fibers to sprout from dorsal root ganglia, and it accelerated the proliferation of Schwann cells.

Animals↗

PubMed2003

Chemistry of the Si-Si and Fe-Fe bonds in the cyclic structure (Me2SiSiMe2)[eta5-C5H4FeCO2]2. Selective cleavage of the Fe-Fe bond by I2 and unexpected properties of the iodide.

The Si-Si bond in the title cyclic structure (1) exhibited unexpected stability toward I(2). Thus, the reaction of 1 with 1 equiv of I(2) in chloroform resulted in selective cleavage of the Fe-Fe bond to afford diiodide (Me(2)SiSiMe(2))[eta(5)-C(5)H(4)Fe(CO)(2)I](2) (2) with retention of the Si-Si bond. When excess (2-4 equiv) I(2) was used to react with 1 in either benzene or chloroform, iodonium-bridged diiron complex [(Me(2)SiSiMe(2))[eta(5)-C(5)H(4)Fe(CO)(2)](2)I(+)](I(5)(-)) (4) was obtained, in which the Si-Si bond was still retained. It is noteworthy that 4 contains a counteranion I(5)(-) rather than the expected I(3)(-), which is the first example for an iodonium-bridged diiron complex to combine a polyiodide anion larger than I(3)(-). UV irradiation of 2 did not affect the stability of the silicon-silicon bond and, in the presence of PR(3), resulted in CO substitution to give (Me(2)SiSiMe(2))[eta(5)-C(5)H(4)Fe(CO)(PR(3))I](2) (5, R = Ph; 6, R = OPh). The molecular structure of 2 was determined by the X-ray diffraction method. It is noteworthy that the structure of 2 does not take the expected anti conformation but adopts a gauche one. The length of the Si-Si bond of 2 [2.353(3) A] is about the same as that of 1 [2.346(4) A], which can be direct evidence to demonstrate that the Si-Si bond in the cyclic structure of 1 is not subject to significant ring strain. The molecular structure of 4 was also determined by the X-ray diffraction method. It is noted that the structure of 4 contains an abnormally large Fe-I(+)-Fe bond angle of 121.25(7) degrees. Of particular interest is the observation that the I(5)(-) anions of 4 are self-assembled into novel layered, two-dimensional networks with the (Me(2)SiSiMe(2))[eta(5)-C(5)H(4)Fe(CO)(2)](2)I(+) cations as the template.

Journal Article↗

PubMed2003

Studies on the synthesis and anti-Osteoporosis of estrogen-GHRPs linkers.

The linkers of estrogen-GHRPs were prepared by the combination of estradiol, estrone, TyrGlyGlyPheLeuOH, and TyrGlyGlyPheLeuOH. Their anti-osteoporosis effect was evaluated by analyzing the data, for instance the weight of the body, femur, femur ash, the content of calcium and phosphor in the femur, the content of calcium and ALP activity in the serum, obtained from the corresponding bioassay in vivo. The results indicated that the anti-osteoporosis potency for estradiol, estrone, TyrGlyGlyPheLeuOH and TyrGlyGlyPheLeuNH(2) may be totally enhanced each other via the corresponding linkers.

Animals↗

PubMed2003

Biomechanical comparison between conventional and rapid expansion of skin.

This study was designed to investigate the effects of different surgical expansion regimens on the biomechanical features of expanded skin. Two hundred and forty millilitres expanders were implanted on the backs of six adult dogs. Six flaps were designed on the dorsum of each dog. After serial expansion, the expander was left beneath the skin for a certain period of time, which is called the maintaining period. Rapid expansion and conventional expansion with various maintaining periods were compared. The experimental result shows that the area gain of expanded skin surface had no significant difference between the rapid and conventional expansion. Both the tension in vivo and the instant stretch-back ratio increased during the expansion, but fell almost to control values after four weeks' maintaining period. Biomechanical properties in vitro, such as tensile strength, stress-strain, stress-relaxation, and creep were tested by INSTRON material testing machine. Results show that the biomechanical properties of expanded specimens differ significantly from those of their controls immediately after expansion. However, the difference reduces with prolongation of maintaining time. With the same maintaining period, the biomechanical properties of rapidly expanded skin are similar to conventionally expanded skin. We conclude that rapid skin expansion did not demonstrate any deleterious effect when compared with the conventional expansion. Extension of the maintaining period can improve the biomechanical properties of expanded skin and effectively reduce the stretch-back ratio. Therefore, rapid expansion with an extended maintaining period is acceptable in clinical practice.

Animals↗

PubMed2003

Biodegradable poly(L-lactide)-poly(ethylene glycol) multiblock copolymer: synthesis and evaluation of cell affinity.

A series of poly(L-lactide)-poly(ethylene glycol) multiblock copolymers (Multi-PLE) with high molecular weight were synthesized and successfully used to fabricate three-dimensional scaffolds. Using mouse NIH 3T3 fibroblasts as model cells, the cell affinity of various Multi-PLE copolymers was evaluated and compared with that of poly(L-lactide) (PLLA) by means of cell attachment efficiency measurement, scanning electron microscopy observation and MTT assay. On one hand, the results showed that the cell attachment efficiency on Multi-PLE 4/1(4/1 refers to the molar ratio of lactidyl units to ethylene oxide units) films was close to that on PLLA film, however, the other Multi-PLE films exhibited much lower cell attachment efficiency than PLLA film, such as Multi-PLE 2/1 and Multi-PLE 1/1, which had higher PEG content. On the other hand, it was interesting to find that cell proliferation on Multi-PLE4/1 and Multi-PLE2/1 scaffolds was better than that on PLLA scaffold, which was closely related to the improved hydrophilicity of Multi-PLE copolymers due to the incorporation of PEG in comparison with pure PLLA. The Multi-PLE copolymer scaffolds with appropriate hydrophilicity were in favor of mass transportation, and then of cell proliferation and cell affinity. It meant that the cell proliferation would be much improved by increasing the hydrophilicity of the three-dimensional scaffolds, which even outweighed the disadvantages of the cell attachment efficiency reduction with the incorporation of PEG.

3T3 Cells↗

PubMed2003

Cell adhesion on gaseous plasma modified poly-(L-lactide) surface under shear stress field.

A series of gases were used for plasma treatment of poly-(L-lactide) (PLLA) under various conditions such as atmosphere, electric power, pressure and time. The NH(3) was preferably selected for modifying the surface of PLLA because it can obtain appropriate hydrophilicity and surface energy with high polar component compared to other gases. Subsequently, cells were seeded onto NH(3) modified surface and exposed to 29.5N/m(2) of shear stress field by means of a parallel plate flow chamber in order to get good insight into the influence of N-containing incorporation on cell retention, cell morphology, and cell shape factor. The results showed that cell retention on the modified PLLA was much higher than that on the unmodified one. The NH(3) plasma modified PLLA with high cell affinity and resistance to shear stress was gained. Surface hydrophilicity, surface energy with high polar component and N-containing groups may play an important role in enhancing cell resistance to shear stress. It revealed that the parallel plate flow chamber is an effective device for evaluating the effects of surface modification on the cell affinity of a material.

3T3 Cells↗

PubMed2003

Developmental aspects of blood-brain barrier (BBB) and rat brain endothelial (RBE4) cells as in vitro model for studies on chlorpyrifos transport.

The mammalian central nervous system (CNS) is characterized by the blood-brain barrier (BBB), a restrictive barrier endowed with the maintenance of homeostatic control of an optimal milieu within the brain. Whereas in tissues other than the CNS, concentrations of various metabolites (amino acids, K+) can undergo frequent fluctuations, the CNS must keep rigorous control over the extracellular cerebral fluid composition, preventing the mirroring of transient fluctuations in blood, because abrupt changes in these metabolites can translate to aberrant CNS function. The BBB is a specialized structure accomplished by individual endothelial cells that are continuously linked by tight junctions. This brief review will address pertinent issues to development of the BBB. Particular emphasis will be directed at the role of astrocytes in the induction and maintenance of the restrictive properties of this barrier, and the utility of in vitro culture models in surveying transport kinetics, exemplified by recent studies with the pesticide, chlorpyrifos.

Animals↗

PubMed2003

GenomeComp: a visualization tool for microbial genome comparison.

We have developed a software tool, GenomeComp, for summarizing, parsing and visualizing the genome sequences comparison results derived from voluminous BLAST textual output. With GenomeComp, the variation between genomes can be easily highlighted, such as repeat regions, insertions, deletions and rearrangements of genomic segments. This software provides a new visualizing tool for microbe comparative genomics.

Computational Biology↗