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Biomedical subjects

H Yuan

Publications and source records attributed to H Yuan.

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

Purification, refolding of hybrid hIFNgamma-kringle 5 expressed in Escherichia coli.

The DNA sequence coding for plasminogen kringle 5 (pK5), an inhibitor of angiogenesis, was fused with that coding for interferon gamma and over-produced in the form of inactive inclusion bodies in E. coli. The amount of fusion protein was about 40% of total protein produced. The fusion protein contained in the inclusion bodies was solubilized in 8 M urea and purified by anion-exchange chromatography. We employed the orthogonal experimental design L16(4(5)) (5 factors, 4 levels, 16 experiments) procedure for researching the influence of denaturant, aggregation suppressor L-arginine, NaCl, pH, and glycine on the refolding procedure. Our results suggest that the presence of appropriate L-arginine, NaCl, and denaturant in the refolding buffer inhibits the aggregation of the fusion protein and increases the yield of renatured protein with biological activity. The refolded fusion protein, gammaIFN/pk5, has in vitro anti-endothelial cell proliferation activity.

Angiogenesis Inhibitors↗
PubMed2001

Material-dependent bone induction by calcium phosphate ceramics: a 2.5-year study in dog.

Bone induction by different calcium phosphate biomaterials has been reported previously. With regard to (1) whether the induced bone would disappear with time due to the absence of mechanical stresses and (2) whether this heterotopically formed bone would give rise to uncontrolled growth, a long-time investigation of porous hydroxyapatite ceramic (HA), porous biphasic calcium phosphate ceramic (TCP/HA, BCP), porous alpha-tricalcium phosphate ceramic (alpha-TCP) and porous beta-tricalcium phosphate ceramic (beta-TCP) was performed in dorsal muscles of dog, for 2.5 years. Histological observation, backscattered scanning electron microscopy observation and histomorphometric analysis were made on thin un-decalcified sections of retrieved samples. Normal compact bone with bone marrow was found in all HA implants (n = 4) and in all BCP implants (n = 4), 48 +/- 4% pore area was filled with bone in HA implants and 41 +/- 2% in BCP implants. Bone-like tissue, which was a mineralised bone matrix with osteocytes but lacked osteoblasts and bone marrow, was found in all beta-TCP implants (n = 4) and in one of the four alpha-TCP implants. Both normal bone and bone-like tissues were confined inside the pores of the implants. The results show that calcium phosphate ceramics are osteoinductive in muscles of dogs. Although the quality and quantity varied among different ceramics, the induced bone in both HA and BCP ceramics did neither disappear nor grow uncontrollably during the period as long as 2.5 years.

Animals↗
PubMed2001

Synthesis and bioactivity of 2,4-diacyl analogues of paclitaxel.

The 2,4-diacyl paclitaxel analogues 8a-8r were prepared from paclitaxel by acylation of 4-deacetyl-2-debenzoylpaclitaxel 1,2-carbonate (3) followed either by hydrolysis of the carbonate and acylation or by direct treatment of the carbonate with an aryllithium. Some of the resulting derivatives showed significantly improved tubulin assembly activity and cytotoxicity as compared with paclitaxel; in some cases this improvement was especially significant for paclitaxel-resistant cell lines.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Low-density lipoprotein receptor-related protein-5 binds to Axin and regulates the canonical Wnt signaling pathway.

To understand how the Wnt coreceptor LRP-5 is involved in transducing the canonical Wnt signals, we identified Axin as a protein that interacts with the intracellular domain of LRP-5. LRP-5, when expressed in fibroblast cells, showed no effect on the canonical Wnt signaling pathway by itself, but acted synergistically with Wnt. In contrast, LRP-5 mutants lacking the extracellular domain functioned as constitutively active forms that bind Axin and that induce LEF-1 activation by destabilizing Axin and stabilizing beta-catenin. Addition of Wnt caused the translocation of Axin to the membrane and enhanced the interaction between Axin and LRP-5. In addition, the LRP-5 sequences involved in interactions with Axin are required for LEF-1 activation. Thus, we conclude that the binding of Axin to LRP-5 is an important part of the Wnt signal transduction pathway.

3T3 Cells↗
PubMed2001

Differential processing of cytosolic and mitochondrial caspases.

The mitochondria have been shown to play a key role in the initiation of caspase activation during apoptosis. Recently, some caspases have been shown to be associated with mitochondria. In this study, we used Jurkat T-lymphoblasts to show that caspases -2 and -3 are located in the mitochondrial intermembrane space, associated with the inner membrane. Caspase-9 is associated with the outer membrane and is exposed to the cytosolic compartment. Caspase activation took place predominantly in the cytosol in response to Fas ligation, but staurosporine treatment led to caspase activation in both cytosol and mitochondria. In response to both Fas and staurosporine treatment, caspase processing could be detected earlier in cytosol than in mitochondria, but this could reflect the limits of sensitive detection by immunoblotting. Only trace amounts of Apaf-1 were found in association with the mitochondria. However, staurosporine treatment led to preferential auto-processing of caspase-9 associated with mitochondria. These findings suggest that mitochondrial caspases are regulated independently of the cytosolic pool of caspases. The data are also consistent with the notion of a caspase nucleation site associated with mitochondria. Using a stable transfected CEM cell line, we show that Bcl-2 suppressed caspase processing in both cytosolic and mitochondrial compartments in response to both staurosporine and Fas ligation.

Journal Article↗
PubMed2001

Use of an osteoinductive biomaterial as a bone morphogenetic protein carrier.

A porous calcium phosphate ceramic, which induced bone formation in soft tissues of dogs, was termed as osteoinductive biomaterial and studied as a carrier of bone morphogenetic protein (rhBMP-2). Cylinder implants (laser spot 4 x 5 mm) impregnated with 0, 1, 10 and 40 microg rhBMP-2 were implanted in dorsal muscles of rabbits for five weeks. Histological observation and histomorphometric analysis were performed on thin un-decalcified sections. No bone formation was detected in the implants without rhBMP-2, while mature lamellar bone was found inside the implants with 1 microg rhBMP-2, both on the outer surface and inside the implants with 10 microg and 40 microg rhBMP-2. Little difference in formed bone was found between 1 microg and 10 microg rhBMP-2, but no difference was found between 10 microg and 40 microg rhBMP-2. A significant difference in bone marrow formation was found among 1, 10 and 40 microg rhBMP-2. The more rhBMP-2, the more bone marrow formed. The present results indicate that osteoinductive biomaterial is a good carrier of BMP and high dose of BMP is not necessary for bone formation in clinic.

Journal Article↗
PubMed2001

Bone formation induced by calcium phosphate ceramics in soft tissue of dogs: a comparative study between porous alpha-TCP and beta-TCP.

Two kinds of tri-calcium phosphate ceramics (Ca/P = 1.50), alpha-TCP and beta-TCP, which has the same macrostructure and microstructure, but different phase composition, were implanted in dorsal muscles of dogs. The samples were retrieved at 30, 45 and 150 days, respectively, after implantation, and were analyzed histologically. There were critically different tissue responses between alpha-TCP ceramic and beta-TCP ceramic. Higher cell populations were observed inside the pores of beta-TCP than those of alpha-TCP, bone tissue was found in beta-TCP at 45 and 150 days, but no bone formation could be detected in any alpha-TCP implants in this study. On the other hand, the bone tissue in beta-TCP seemed to degenerate at 150 days. The results indicate that porous beta-TCP can induce bone formation in soft tissues of dogs; while the rapid dissolution of the ceramic and the higher local Ca2+, PO(4)3- concentration due to the rapid dissolution of alpha-TCP may resist bone formation in alpha-TCP and the less rapid dissolution of beta-TCP may be detrimental to already formed bone in beta-TCP.

Journal Article↗
PubMed2001

Biological sample analysis with immunoaffinity solid-phase microextraction.

A theophylline antiserum was covalently immobilized on the surface of a fused silica fiber, modified with 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde, and used as a selective and sensitive extraction medium for the immunoaffinity solid-phase microextraction (SPME) determination of theophylline in serum samples. The specificity of the immunoaffinity SPME fiber was first investigated using a fixed concentration of [3H]theophylline together with various amounts of interference, possessing no cross-reactivity with the theophylline antibody. No significant non-specific binding was observed. The reproducibility of the fiber preparation and the immunoaffinity SPME analysis was also investigated, resulting in a relative standard deviation of 6.1% for five analyses of the same fiber. The antigen-antibody binding isotherm was obtained by analyzing theophylline standards of various concentrations (0.1-5 ng mL(-1)) until saturation values were reached. Initial binding of theophylline was linear with a r2 = 0.968. The cross-reactivity of the theophylline immunoaffinity SPME fiber for the structural analog caffeine was investigated by adding various amounts of caffeine in the presence of theophylline at a saturation concentration and produced a low cross-reactivity value of 0.1%. Finally. spiked serum samples (10 and 50 ng mL(-1)) were successfully analyzed with an excellent correlation with the standard binding isotherm, thus confirming the performance of the immunoaffinity SPME coating for improved bioanalysis.

Animals↗
PubMed2001

Aminopeptidase A: a nephritogenic target antigen of nephrotoxic serum.

BACKGROUND: We investigated potential targets of antibody-mediated glomerular injury induced with a noncomplement binding fraction of sheep anti-rat nephrotoxic serum (NTS). This model is characterized by severe complement- and leukocyte-independent proteinuria within 24 hours of NTS injection into rats. METHODS: NTS-reactive glomerular cell and matrix proteins were identified by immunoprecipitation, Western blot analysis, protein sequencing, cDNA library screening, and enzyme-linked immunosorbent assay. Proteinuria was measured in rats injected with NTS from which reactivity against type IV collagen had been removed by immunoadsorption, and antibodies were eluted from the glomeruli of proteinuric rats that had been injected with unabsorbed NTS. Having identified aminopeptidase A (APA) as a major target of NTS, we studied the effect of NTS and anti-APA on mouse glomerular epithelial cells in culture. RESULTS: NTS identified several podocyte and matrix proteins; however, APA was the only cell surface protein reactive with antibodies eluted from the glomeruli of rats injected with NTS. Although the eluate also contained reactivity to the noncollagenous domains of alpha1 and alpha3 chains of type IV collagen, immunodepletion of these antibodies did not diminish the ability of NTS to cause proteinuria. We also documented the surface expression of APA on mouse glomerular epithelial cells in culture, and found that NTS and specific anti-APA antibodies induce a time- and temperature-dependent redistribution of the antigen. CONCLUSIONS: APA, a type II integral membrane metallopeptidase, is a major target of NTS in vivo and is known to be present on the surface of podocytes. NTS-induced proteinuria is independent of reactivity to known nephritogenic matrix proteins. These findings, in combination with previous studies showing that monoclonal anti-APA antibodies induce severe proteinuria in mice, suggest that anti-APA antibodies are responsible for complement-independent proteinuria in this model.

Aminopeptidases↗
PubMed2001

Alkaloids and flavonoids from peanut skins.

Separation of the water-soluble fraction of peanut skins led to the isolation of 8 flavonoids and two novel indole alkaloids. Two new flavonoid glycosides have been identified as isorhamnetin 3-O-[2-O-beta-glucopyranosyl-6-O-alpha-rhamnopyranosyl]- beta-glucopyranoside and 3',5,7-trihydroxyisoflavone-4'-methoxy-3'-O-beta-glucopyranoside. Two alkaloids are 2-methoxyl-3-(3-indolyl)-propionic acid and 2-hydroxyl-3-[3-(1-N-methyl)-indolyl]-propionic acid. These isolated flavonoids were evaluated for their free radical scavenging activity and protein glycation inhibitory effects.

Alkaloids↗
PubMed2001

Immunization with a pentameric L1 fusion protein protects against papillomavirus infection.

The prophylactic papillomavirus vaccines currently in clinical trials are composed of viral L1 capsid protein that is synthesized in eukaryotic expression systems and purified in the form of virus-like particles (VLPs). To evaluate whether VLPs are necessary for effective vaccination, we expressed the L1 protein as a glutathione S-transferase (GST) fusion protein in Escherichia coli and assayed its immunogenic activity in an established canine oral papillomavirus (COPV) model that previously validated the efficacy of VLP vaccines. The GST-COPV L1 fusion protein formed pentamers, but these capsomere-like structures did not assemble into VLPs. Despite the lack of VLP formation, the GST-COPV L1 protein retained its native conformation as determined by reactivity with conformation-specific anti-COPV antibodies. Most importantly, the GST-COPV L1 pentamers completely protected dogs from high-dose viral infection of their oral mucosa. L1 fusion proteins expressed in bacteria represent an economical alternative to VLPs as a human papillomavirus vaccine.

Animals↗
PubMed2001

Inhibition of host transcription by vesicular stomatitis virus involves a novel mechanism that is independent of phosphorylation of TATA-binding protein (TBP) or association of TBP with TBP-associated factor subunits.

The matrix (M) protein of vesicular stomatitis virus (VSV) is a potent inhibitor in vivo of transcription by all three host RNA polymerases (RNAP). In the case of host RNA polymerase II (RNAPII), the inhibition is due to lack of activity of the TATA-binding protein (TBP), which is a subunit of the basal transcription factor TFIID. Despite the potency of M protein-induced inhibition in vivo, experiments presented here show that M protein cannot directly inactivate TFIID in vitro. Addition of M protein to nuclear extracts from uninfected cells did not inhibit transcription activity, indicating that the inhibition is indirect and is mediated through host factors. The host factors that are known to regulate TBP activity include phosphorylation by host kinases and association with different TBP-associated factor (TAF) subunits. However, TBP in VSV-infected cells was found to be assembled normally with its TAF subunits, as shown by ion exchange high-pressure liquid chromatography and sedimentation velocity analysis. A normal pattern of phosphorylation of TBP in VSV-infected cells was also observed by pH gradient gel electrophoresis. Collectively, these data indicate that M protein inactivates TBP activity in RNAPII-dependent transcription by a novel mechanism, since the known mechanisms for regulating TBP activity cannot account for the inhibition.

DNA-Binding Proteins↗
PubMed2001

[A permanent implantable pulsatile impeller heart with a specially devised needle bearing].

The author's implantable pulsatile impeller pump can assist the circulation of the calves for several months. The termination of the experiments was related to wear of the mechanical bearing, which resulted in vibration of the rotor and pump failure. It seemed as if the experiments could have lasted indefinitely if the bearing had not failed. To solve the problem of bearing wear, a specially devised rolling bearing was investigated and applied to the impeller pump. Its service life is more than 10 years due to the wear-proof roller made of ultra-highmolecular weight polythene. This newly devised impeller heart promises to have long-term and permanent applications. Compared with the magnetic bearing, the rolling bearing has the advantages of simpler construction and control, no consumption of energy, and better reliability.

Animals↗
PubMed2001

[Pulsatile rotary pumps with low hemolysis].

As is well known, a pulsatile flow is important in assisted-circulation but it is difficult to produce a pulsatile flow with rotary pump, because excessive hemolysis will be generated. The authors have found that the turbulent shear is the main factor for red cell damage and therefore the key point of pulsatile rotary pumps is to reduce the turbulence by producing a pulsatile flow. In the authors' pulsatile axial pump, the pulsatile flow is obtained by axial reciprocation of constant rotating impeller; the rotation and reciprocation of the impeller are driven separately by a DC motor and a pneumatic device. Though a physiological pulsatile flow could be achieved and turbulence would not increase remarkably because the impeller rotates constantly, a second driver except a DC motor is nevertheless necessary, thus the system will become complicated. In the authors' pulsatile radial pump, a pulsatile flow is achieved by changing the rotating speed of the impeller periodically. Turbulence is minimized by a special design of twisted vanes which enable the blood flow to change its direction rather than its dimension during periodic change of rotating speed. Hemolysis tests demonstrated that the index of hemolysis(IH) of the author's pulsatile radial pump is 0.020, with is slightly more than that of the author's nonpulsatile radial pump(IH = 0.015). Animal experiments indicated that the pulsatile radial pump can assist the circulation of calves for several months without harm to blood elements and organ functions of the recipients.

Animals↗
PubMed2001

[Sequence analysis of mtDNA 12S rRNA, tRNA(Leu(UUR)),tRNA(Ser(UCN))and 16S rRNA gene of 12 nonsyndromic inherited deafness pedigrees].

OBJECTIVE: To detect the relationship of mtDNA mutation with inherited deafness and the reason for pedigree's hypersensitivity to ototoxicity of aminoglycoside antibiotics(AmAn). METHODS: Pedigree investigations were conducted. The blood samples were obtained from 12 pedigrees, and DNA was extracted from the isolated leukocytes. After that, mtDNA fragments were amplified by PCR. The 1555(G), 3243(G) and 7445(G) mutations were detected by Alw 26 I, Apa I and Xba I restriction endonuclease digestion respectively, and then sequencing of 12S rRNA, tRNA(Leu(UUR)), tRNA(Ser(UCN))and 16S rRNA gene was performed. RESULTS: Restriction endonuclease digestion and sequence analysis showed that all the pedigrees carried mtDNA mutation, among them, 10 pedigrees carried 1555(G) mutation; 2 pedigrees, 7445(G) mutation; no pedigree was found to harbor the 3243(G) mutation. Sequence analysis of 16S rRNA gene showed that the mutations are 2230(G), 2230(AG), 2243(AG), 2230(AA). CONCLUSION: The pedigrees that carried 1555(G) or 7445(G) mutation showed hereditary or congenital hearing loss. The 1555(G) or 7445(G) mutation in association with 16S rRNA gene mutation led to pedigree's hypersensitivity to AmAn ototoxicity.

Base Sequence↗
PubMed2001

Primary studies on heroin abuse and injury induced by oxidation and lipoperoxidation.

OBJECTIVE: To further reveal serious risks of heroin abuse to human body and clarify grave injuries of oxidation, peroxidation and lipoperoxidation induced by nitric oxide and other free radicals to heroin abusers. METHODS: Determined and compared plasma levels of nitric oxide (P-NO), vitamin C (P-VC), vitamin E (P-VE), beta-carotene (P-beta-CAR), lipoperoxides (P-LPO) and erythrocyte activities of superoxide dismutase (E-SOD), catalase (E-CAT), glutathione peroxidase (E-GSH-Px) and erythrocyte level of lipoperoxides (E-LPO) in 137 cases of heroin abusers (HAs) and 100 cases of healthy volunteers (HVs), used linear regression and correlation, stepwise regression and correlation to analyze correlation among heroin-abusing-duration (HAD), daily-heroin-abusing-quantity (DHAQ) with above determination values in the HAs. RESULTS: Compared with the above average values in the HVs group, the average values of P-NO, P-LPO, E-LPO in the HAs group were significantly increased (P < 0.0001), the average values of P-VC, P-VE, P-beta-CAR, E-SOD, E-CAT and E-GSH-Px were significantly decreased (P < 0.0001); the analysis of linear regression and correlation showed that with ascending of the HAD and DHAQ in the HAs, the values of P-NO, P-LPO, E-LPO were gradually increased (P < 0.0001), the values of P-VC, P-VE, P-beta-CAR, E-SOD, E-CAT, E-GSH-Px were gradually decreased (P < 0.0001); the analysis of stepwise regression and correlation suggested that the correlation among the HAD, DHAQ with the values of P-NO, P-VC, P-VE was the closest. CONCLUSION: The balance between oxidation and antioxidation in the HAs was seriously destroyed, and the injuries induced by nitric oxide and other free radicals, oxidation, peroxidation and lipoperoxidation reactions to the body of HAs gravely exacerbated. In the abstaining from heroin dependence, therefore, it should consider that sufficient quantum antioxidants such as VC, VE and beta-CAR are dosed to the HAs so as to abate the injuries to their bodies.

Adult↗