Biomedical subjects

Y Lin

Publications and source records attributed to Y Lin.

At least 307 records · Page 17Linked to original sources

PubMed1999

[A comparative study of mechanical properties of microwave-cured and conventional water bath-cured denture base resins].

OBJECTIVE: To study the mechanical properties of microwave-cured polymethyl methacrylate (PMMA) denture base resins. METHODS: Using experiment research, the mechanical properties of microwave-cured and water bath-cured PMMA materials were compared. RESULTS: The microwave-cured acrylic strips had equal or better mechanical properties than conventionally processed strips. CONCLUSION: The microwave-cured denture materials satisfies the requirements of the prosthetic clinic.

Biomechanical Phenomena↗

PubMed1999

[Molecular cloning of rat OB gene and its expression in Escherichia coli].

In order to provide rat OB gene product for studying the relationship between obesity and noninfectious diseases, rat OB cDNA was amplified by RT-PCR technique. 460 bp fragment of OB cDNA was subcloned into EcoRI/BamHI site of plasmid pUC 19. Sequence analysis of OB cDNA revealed that the translation reading frame was identical with that reported in the literature. Thereby plasmid pBV220-rOB was constructed and the specific expression of OB gene in E. coli identified by SDS-PAGE electrophoresis was obtained.

Amino Acid Sequence↗

PubMed1999

[Expression of a HCV multi-epitopes antigen gene and study on its immunogenicity].

Due to the hypervariable character of hepatitis C virus (HCV), 5 conserved T and/or B cell epitopes from core, envelope, NS3 and NS5 protein of HCV were chosen to form a 270 bp multi-epitopes antigen gene. The gene was clone into a fusion vector pWR450-1 to express a beta-galactosidase-HCV hybrid protein GZ-PCX. The purified GZ-PCX protein was specifically recognized by human anti-HCV antibodies. These results show that the HCV hybrid multi-epitopes antigen has excellent immunogenicity, which might be able to be used as an effective diagnosis agent and to provide protectivity to any genotype of HCV which might partly solve the problems in the researches of HCV vaccines.

Epitopes↗

PubMed1999

[The inhibitory effect of selenite and other antioxidants on the complement mediated experimental pulmonary alveolitis].

OBJECTIVE: To test the regulatory effect of selenite and other antioxidants on complement PMN activation feedback mechanism mediated inflammatory response in experimantal pulmonary vasculitis. METHODS: Mouse model of pulmonary Arthus reaction vasculitis developed with BSA sensitization and antigen inhalation was used for tests of inhibitory effect of oral administration of sodium selenite, glycyrrhizin flavonoids and/or vitamin E on the incidence of developing vasculitis, which could reflect the modulation of inflammatory response and tissue injury. RESULTS: A remarkable inhibitory effect of selenite or combined flavonoid and vitamin E on the induction of pulmonary vasculitis were observed as the incidence of vasculitis could drop from 100% of the untreated group down to 25% of the antioxidants treated groups, revealing modulation of inflammatory response. CONCLUSIONS: It indicated a newer insight into mechanism of the inflammatory response could give a novel approach to the modulation of inflammatory response. An adjuvant therapy of selenium and antioxidants to the interventions of inflammatory disorders has been expected.

Animals↗

PubMed1999

[Aspirin inhibited the adhesion of platelets to neutrophil in patients with acute myocardiac infarction].

OBJECTIVE: To investigate the effect and mechanism of aspirin(ASA) on platelet-neutrophil adhesion. METHODS: Using rosette forming assay to observe the effect of ASA on the binding of platelets to neutrophil and radioimmunoassay to observe the effect of ASA on the thrombin-induced expression of GMP-140 on the surface of human platelets. RESULTS: Patients with acute myocardial infarction showed a significant increase in neutrophil-platelet adhesion (63.3 +/- 7.8)%, (n = 20, P < 0.001) as compared with normal subjects(16.5 +/- 2.6)% (n = 20). Thrombin promoted adhesion by increasing the expression of GMP-140 on the surface of human platelets. When the concentration of thrombin was 0.5 U/ml, the rate of neutrophil-platelet adhesion and the number of molecular of GMP-140 on the surface of platelet was (64.2 +/- 4.2)%, and (1.80 +/- 0.20) x 10(3) per platelet respectively. At high concentration, ASA significantly inhibited thrombin (0.5 U/ml) stimulated platelets binding to neutrophils and expressing GMP-140 on their surface. When the final concentration of ASA was 500,5000 micrograms/ml, the ratio of thrombin-stimulated platelets binding neutrophils was (34.7 +/- 3.8)%, (21.2 +/- 3.6)% respectively (n = 20, P < 0.01); the number of molecular of GMP-140 expressing on the surface of platelet was (1.02 +/- 0.24) x 10(3), (0.68 +/- 0.18) x 10(3) per platelet respectively (n = 9, P < 0.001). CONCLUSIONS: It contributes to the antithrombosis of ASA that inhibiting platelet-neutrophil adhesion by down expression of GMP-140 on the surface of human platelets.

Aspirin↗

PubMed1999

[Gastrointestinal inhibitory effects of sesquiterpene lactones from Atractylodes macrocephala].

Atractylenolide I (8,9-dehydroasterolide, B), 4,15-epoxy-8 beta-hydroxyasterolide (C) and atractylenolide III (8 beta-hydroasterolide, D) from Atractylodes macrocephala Koidz, 28.0, 56.0 mumol/L, inhibited the spontaneous movement of rat isolated ileum with contractile force decreased obviously (P < 0.001), but the rest force not affected (P > 0.05). B, C and D inhibited the spasm enhanced by Ach and His to rat ileum, rightly shifted the dose-response curves and reduced the maximal response (P < 0.05). Pretreatment with B, C or D 28.0, 56.0 mumol/L Ver 0.28 mumol/L significantly antagonized CaCl2-induced contraction of rat isolated ileum. Co bathing of B, C or D 56.0 mumol/L with Atr 0.19 mumol/L weakened the response of ileum to Ach. B, C or D 56.0 mumol/L restrained the spasm of ileum mediated by Neo 2.15 mumol/L. The modified Phenol Red Paste Model demonstrated that B, C or D in dose of 28.0 mg/kg inhibited the gastrointestinal prochoresis of mice significantly. These results suggested that B, C and D inhibit the gastrointestinal movement of rat and the spasm induced by the agonists. Their activities are related to the inhibition of cholinergic system and Ca2+.

Animals↗

PubMed1999

[The improvement on related condition of corneal cryopreservation and roles of cryopreserved corneas in emergent keratoplasty].

PURPOSE: To study the cryopreserved corneal endothelium viability on the condition that a series of related factors on long-term corneal cryopreservation were modified. The frozen corneas were used for emergent penetrating keratoplasty on poor condition patients. To evaluate the role of cryopreserved corneas on clinical application, especially on emergent keratoplasty. METHODS: Residual peripheral corneas were stained with Trypan blue and Alizarin red in order to assess endothelium survival rate after central grafts were punched. Specular microscope was used to measure corneal thickness and count endothelium density. The transparent rate of grafts, infective control rate, retinal restorative rate and the recovery degree of visual acurity were emphasized respectively. RESULTS: Endothelium survival rate of grafts was 82.1% averagely. Postoperative endothelium density was 1,642 cells/mm2 and graft thickness was 0.59 mm averagely. The epithelial defects healed after 2-5 days of the operation and edematous grafts were reclear after 2-4 weeks of the operation in all grafts, except for chemical burn and thermal burn. The transparent rate was 87.5%. Infective controll rate was 90.63%. Retinal restorative rate was 55.56%. Some useful visual acurity can be obtained when the infection was under controlled and the retinal was reattached. CONCLUSION: Modified long-term corneal cryopreservation is effective in maintaining endothelium viability and integrity. Furthermore, it could provide donors anytime because of it's unlimited preservative duration. Our study emphasizes especially the role of cryopreserved corneas in emergent keratoplasty.

Adolescent↗

PubMed1999

[Study of conformation of serum albumin by FTIR].

This paper used the FTIR method to study the spectra of bovine serum albumin (BSA) and its solution. The secondary structure and conformation was assigned by FTIR-deconvolution analysis. The result indicated that BSA secondary structure in solid is different from in aqueous solution. As the decrease of BSA concentration from 3.241 x 10(-1) to 4.032 X 10(-2) g X mL(-1), the amide I band components at 1 609.84, 1 633.85,1 653.69, 1 681.16 and 1 694.88 cm(-1) shifted to 1 608. 24, 1 638.36, 1 656.10, 1 674.87 and 1 690.78 cm(-1), respectively, the component at 1 621.50 cm(-1) unchanged.

Animals↗

PubMed1998

The hepatitis B virus X protein is a co-activator of activated transcription that modulates the transcription machinery and distal binding activators.

Hepatitis B virus X protein (HBx) transactivates viral and cellular genes through a wide variety of cis-elements, but the mechanism has not been well elucidated. Evidence for nuclear events in HBx transactivation has been reported. Here we examine the role of HBx in modulation of transcription with a transient transfection system and an in vitro transcription assay. Reporters bearing Gal4-binding sites were applied to avoid the effects of endogenous transcription factors with or without signaling processes. The Gal4-DNA binding domain fused form of HBx exhibited no effect on Gal4-responsive reporters. However, HBx augmented activated transcription by transcriptional activators, suggesting HBx retains a co-activator but not a transcriptional activator function. The functional domain for co-activation was the same as that for HBx transactivation, and the transcription factor IIB- and RNA polymerase II subunit 5-interacting sites of HBx, which were critical for HBx transactivation, were shown to be crucial for the co-activation function. Importantly, HBx stimulated transcription on templates bearing the X responsive elements in vitro with endogenous activators. These results imply that HBx acts as a co-activator that modulates transcriptional machinery and distal-binding activators, which may explain one of the mechanisms of transactivation by HBx when localized in nuclei.

DNA-Directed RNA Polymerases↗

PubMed1998

Sustained exposure to a glycine receptor partial agonist differentially alters NMDA receptor agonist and antagonist potencies in cultured spinal cord neurons.

Sustained (20 h) exposure to the glycine partial agonist 1-aminocyclopropanecarboxylic acid (ACPC) significantly reduced N-methyl-D-aspartate (NMDA)-induced neurotoxicity in cultured spinal cord neurons when the NMDA (25 and 100 microM) was added to the cultures 30 min after removal of the ACPC (1 mM). In contrast, ACPC preexposure failed to protect against kainate-induced neuronal injury. The magnitude of neuronal protection against NMDA (100 microM) was further enhanced if the neurons pretreated with ACPC were reexposed to this drug during the NMDA challenge. In addition, the potencies of both the competitive NMDA antagonist AP5 and the noncompetitive antagonist dizocilpine to block NMDA toxicity were significantly increased following ACPC preexposure, while the potency of the competitive glycine receptor antagonist 7-chlorokynurenate (7-CK) was unchanged. Analysis of Northern blots suggest that ACPC-induced changes in NMDA receptor function were not associated with alterations in the levels of the mRNAs encoding the NMDAR-1, -2A, -2B, or -2C subunits. These results indicate that sustained exposure to ACPC modifies NMDA receptors in a manner that diminishes NMDA receptor-mediated neurotoxicity while selectively enhancing the potencies of several NMDA receptor antagonists. These effects do not appear to be related to changes in expression of specific NMDA receptor subunits, and may instead involve a post-translational modification of one or more subunit proteins.

2-Amino-5-phosphonovalerate↗

PubMed1998

A microfabricated dialysis device for sample cleanup in electrospray ionization mass spectrometry.

A laser microfabricated device was constructed for rapid microdialysis cleanup of biological samples for analysis by electrospray ionization mass spectrometry (ESI-MS) in both off-line and on-line modes. A microdialysis membrane was sandwiched between two chips having micromachined serpentine channels. The total volume of the sample serpentine channel used for the microdialysis was 1 microL. Efficient desalting was demonstrated for both DNA and protein samples using ESI with an ion trap mass spectrometer after microdialysis against a counter flow of ESI-compatible buffer. Signal-to-noise ratios were also greatly enhanced compared to direct infusion of the original nondialyzed samples. Importantly, the microfabricated device allowed use of sample flow rates 1 order of magnitude smaller than previous designs based on a microdialysis fiber, allowing reduced sample utilization and improved sensitivity with ESI-MS. The effectiveness of the cleanup was attributed to the size difference between the sample channel and the buffer channel and the fact that the sample is continuously refreshed by the buffer counterflow. The results indicate substantial potential for construction of highly compact and rugged devices enabling field applications of ESI-MS.

DNA↗

PubMed1998

Staining of cell surface human CD4 with 2'-F-pyrimidine-containing RNA aptamers for flow cytometry.

We have used recombinant human CD4 presented on beads as an affinity matrix to screen a 2'-F-pyrimidine-containing RNA library with a complexity of approximately 10(14) molecules. Affinity-selected aptamers bind recombinant CD4 with low nanomolar equilibrium dissociation constants. These high-affinity aptamers conjugated to different fluorophores such as fluorescein and phycoerythrin were used to stain cells, expressing human CD4 on cell surface, for analysis by flow cytometry. Aptamers, conjugated to fluorophores, stained mouse T cells that express human CD4 on the surface, but not the control mouse T cells lacking human CD4. The control cells, however, do express mouse CD4 whose extracellular domain has 55% sequence identity to the human form. These human CD4-specific aptamers selectively stained CD4(+) T cells in a preparation of human peripheral blood mononuclear cells. These results and others suggest that aptamers are emerging as a versatile class of molecules that can be used for various diagnostic applications performed under different formats or platforms.

Amino Acid Sequence↗

PubMed1998

N-terminal myosin-binding fragment of talin.

Talin, an actin-binding protein from smooth muscle, is shown to bind to myosin in such a way that it stimulates the ATPase activity of myosin irrespective of the phosphorylation state of myosin. The binding site is shown to be localized at the N-terminal, 47 KDa fragment. The position of the actin-binding site at the C terminal suggests that talin may work as a crosslinker between myosin and actin.

Actins↗

PubMed1998

Improved internal defibrillation success with shocks timed to the morphology electrogram.

BACKGROUND: A previous retrospective study by our group suggested that shocks timed to the upslope of the shocking lead electrogram improved defibrillation efficacy. The goal of this study was to prospectively determine whether defibrillation threshold could be reduced by use of an algorithm that timed shocks to the upslope of coarse ventricular fibrillation (test treatment) compared with shocks delivered asynchronously after 10 seconds of fibrillation (control treatment). METHODS AND RESULTS: Ten pigs were instrumented with a 3-lead system for internal defibrillation. Initial estimates of the energy required to achieve defibrillation E50 for both treatments were made by an up/down method. Subsequently, additional shocks at V50+/-10% and V50-20% were given for each treatment to obtain data points at higher and lower intensities. Probability-of-success curves were estimated for both treatments by the best-fit method. Energies required were significantly lower for the timed shocks than for the asynchronous shocks (P<0.00 1). E80 was reduced 15.5%, from 27.1+/-2.5 to 22.9+/-1.8 J (P<0.002). The width of the probability-of-success curve (E80-E20) for the test treatment was also significantly narrower than that for the control treatment (7.1+/-0.9 versus 10.8+/-1.7, P<0.01). Normalized curve width (E80-E20)/E50 was decreased from 51+/-5% of E50 for control shocks to 37+/-4% of E50 for synchronous shocks (P<0.02). CONCLUSIONS: In this model, defibrillation threshold is lower and more deterministic when shocks are timed to the upslope of the shocking lead electrogram. If a similar reduction is observed in humans, shock timing may lower defibrillation threshold and simplify programming of shock intensity.

Algorithms↗

PubMed1998

Structure-function studies on positions 17, 18, and 21 replacement analogues of glucagon: the importance of charged residues and salt bridges in glucagon biological activity.

We have designed and synthesized eight compounds 2-9 which incorporate various amino acid residues in positions 17, 18, and 21 of the glucagon molecule: 2, [Lys17]glucagon amide; 3, [Lys18]glucagon amide; 4, [Nle17,Lys18,Glu21]glucagon amide; 5, [Orn17,18, Glu21]glucagon amide; 6, [d-Arg17]glucagon; 7, [d-Arg18]glucagon; 8, [d-Phe17]glucagon; and 9, [d-Phe18]glucagon. Compared to glucagon (IC50 = 1.5 nM), analogues 2-9 were found to have binding affinity IC50 values (in nM) of 0.7, 4.1, 1.0, 2.0, 5.0, 25.0, 43.0, and 32.0, respectively. When these compounds were tested for their ability to stimulate adenylate cyclase (AC) activity, they were found to be full or partial agonists having maximum stimulation values of 100, 100, 100, 100, 87, 78, 94, and 100%, respectively. On the basis of the X-ray crystal structure of [Lys17,18,Glu21]glucagon amide reported here, the ability to form a salt bridge between Lys18 and Glu21 is probably key to their increased binding and second messenger activities. Among the eight analogues synthesized here, only analogue 4 preserves the ability to form a salt bridge between Lys18 and Glu21. However, since these modifications are minor they do not seem to change the amphiphilic character of the C-terminus, allowing these analogues to reach 78-100% stimulation in the adenylate cyclase assay. Biological data from analogues 6-9 supports the idea that position 18 of glucagon may influence binding only, while position 17 may influence both receptor recognition and transduction.

Adenylyl Cyclases↗

PubMed1998

Detection of telomerase activity in prostate needle-biopsy samples.

BACKGROUND: Telomerase in an enzyme ribonucleoprotein responsible for cell immortality and oncogenesis. Telomerase activity has been detected in most cancers, including prostate cancer. To verify whether the detection of telomerase in prostate needle biopsy samples could have diagnostic value, we blindly assayed telomerase activity in samples from patients who were clinically suspected of having prostate cancer. METHODS: A total of 183 prostate biopsy samples was obtained from 63 patients who were suspected of having prostate cancer. Telomerase activity was determined by polymerase chain reaction (PCR)-based telomeric repeat amplification protocol (TRAP) assay. An internal telomerase assay standard (ITAS) was used in this study to distinguish false negatives. RESULTS: Telomerase activity was detected in 17 of 19 (89.5%) patients with prostate cancer (chi(2) test, P < 0.005). In 39 of 42 (92.9%) biopsy samples from these 19 prostate cancer patients, confirmed histologically as prostate cancer, telomerase activity (chi(2) test, P < 0.005) was detected. Meanwhile, we also found one false-positive sample. In contrast, all of 44 normal or benign prostate disease patients (124 biopsy specimens) were telomerase-negative. We also revealed that poorly differentiated prostate cancer often expresses a high level of telomerase activity. The area of cancer tissue in biopsy specimens was not associated with relative telomerase activity. CONCLUSIONS: This study suggests that determination of telomerase activity in prostate needle-biopsy samples might be a useful tool for detecting prostate cancer.

Adenocarcinoma↗

PubMed1998

Interfacial recognition by bee venom phospholipase A2: insights into nonelectrostatic molecular determinants by charge reversal mutagenesis.

The basis for tight binding of bee venom phospholipase A2 (bvPLA2) to anionic versus zwitterionic phospholipid interfaces is explored by charge reversal mutagenesis of basic residues (lysines/arginines to glutamates) on the putative membrane binding surface. Single-site mutants and, surprisingly, multisite mutants (2-5 of the 6 basic residues mutated) are fully functional on anionic vesicles. Mutants bind tightly to anionic vesicles, and active-site substrate and Ca2+ binding are not impaired. Multisite mutants undergo intervesicle exchange slightly faster than wild type, especially in the presence of salt. It is estimated that electrostatic contribution to interfacial binding is modest, perhaps 2-3 kcal/mol of the estimated 15 kcal/mol. Elution properties of bvPLA2 from HPLC columns containing solid phases of tightly packed monolayers of phosphocholine amphiphiles suggest that ionic effects provide a modest portion of the interfacial binding energy and that this contribution decreases as the number of cationic residues mutated is increased. These results are consistent with the observation that Gila monster venom PLA2 (Pa2), which is homologous to bvPLA2, has high activity on anionic vesicles despite the fact that it has only a single basic residue on its putative interfacial recognition face. Results with bvPLA2 mutants show that manoalogue and 12-epi-scalaradial inactivate bvPLA2 by modification of K94. Also, deletion of the large beta-loop (residues 99-118) is without consequence for interfacial binding and catalysis of bvPLA2. All together, the preferential binding of bvPLA2 to anionic vesicles versus phosphatidylcholine vesicles is mainly due to factors other than electrostatics. Therefore hydrogen-bonding and hydrophobic interactions must provide a major portion of the interfacial binding energy, and this is consistent with recent spectroscopic studies.

Animals↗

PubMed1998

Fourier transform infrared (FT-IR) spectroscopic studies of peptide models for interaction of the binding regions of high molecular weight kininogen and prekallikrein.

The binding sites for high molecular weight kininogen (HK) on prekallikrein (PK) are composed of two discontinuous segments in the primary sequence, one in Apple 1 domain (PK56=F56-G86) and the other in Apple 4 (PK266=K266-G295). The site on HK, HK31, is subsumed in a 31-amino-acid sequence (S565-K595) near the C-terminus which has the same affinity for prekallikrein as the entire HK molecule. The binding among them is likely due to conformational changes which serve to juxtapose the PK binding domain within HK with the HK binding site. Resolution-enhanced Fourier transform infrared spectroscopy (FT-IR) has been employed to analyze the contents of secondary structural elements of PK56 and HK31 and to reveal the possible specific binding portion and structural changes in HK31 and PK56 upon binding. From the amide I bands of their deconvoluted FT-IR spectra, it is known that PK56 contains no helix component, while HK31 has two different helical conformations. A quantitative comparison of the spectra of HK31, PK56 and their binding complex suggests that the conformation of 3(10)-helix in HK31 has been changed to an alpha-helix, and one disordered segment of PK56 may have been changed to extended conformation. The other structural components in PK56 and HK31 remain unchanged. Since previous studies have shown that these peptides mimic the natural protein in their bioactivity, their interaction may reflect similar changes in the natural molecules.

Amino Acid Sequence↗