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Biomedical subjects

Y Duan

Publications and source records attributed to Y Duan.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Changes in t-PA, PAI-1 gene expression of coronary arteries with preconditioning in acute myocardial infarction rat].

The changes of t-PA, PAI-1 gene expression and t-PA activity were investigated in coronary arteries of Acute Myocardial Infarction (AMI) rat by nucleic acid molecular hybridization and spectrophotometric assay. The effect of preconditioning on t-PA and PAI-1 was observed in this model. The results indicated that: (1) Tissue t-PA activity in ischemia was significantly decreased than that in control (P < 0.01). t-PA activity was obviously increased in preconditioning group (P < 0.01 compared with ischemia group). (2) t-PA and PAI-1 mRNA expression in ischemia were higher than that in control, especially PAI-1 4.6 times higher than that in control), while PAI-1 expression lower in preconditioning rat. (3) In situ hybridization showed t-PA and PAI-1 were primarily expressed by endothelial cells in vessels of rat heart. These data suggested that abnormal expression of PAI-1 and t-PA was involved in AMI. This fibrinolytic depress was associated with high PAI-1 expression. Preconditioning may be effective to protect myocardium through decreasing PAI-1 mRNA expression.

Animals↗
PubMed1997

[Subtype and sequence analysis of the C2-V3 region of gp120 genes among human immunodeficiency virus infected IDUs in Ruili epidemic area of Yunnan Province of China].

DNA fragments of HIV-1 env gene were amplified by nested-PCR from 17 uncultured peripheral blood mononuclear cells (PBMCs) obtained from HIV-1 seropositive intravenous drug users (IDUs) in Ruili city of Yunnan Province. The C2-V3 region (about 450 bp) of them were sequenced. Sequence analysis showed that there exists two HIV-1 subtypes, B and C, with 5.8% and 2.2% gene divergence inside each subtype. The 12 subtype B strains, were closely related to those found in Thailand, Myanma and Ruili city of Yunnan, and the nucleotide sequence divergence between them ranged from 4.4% to 4.9%; meanwhile, the 5 subtype C strains were most close to those found in India as well as Ruili city, all with a genetic distance of 1.9%. The small divergence among Ruili HIV-1 subtype C strains suggests a recent epidemic. The analysis of V3 loop amino sequence of 12 subtype B HIV-1 reveals that V3-tip motif of 6 samples (50%) is GPGQ and that of 3 samples (25%) is GPGR. In addition, the codon of arginine (R) of all the strains is CGA instead of AGA. This result is in accordance with our previous hypothesis that there is a drift in vivo from GPGR to GPGQ motif on the tipof V3-loop of HIV-1 subtype B strain in this arm with the elapse of time.

Amino Acid Sequence↗
PubMed1997

Preliminary study of the effects of metoprolol and propafenone on ventricular arrhythmia with positive ventricular late potential.

OBJECTIVE: To compare the effects of metoprolol and propafenone in patients with ventricular arrhythmia (VA) of positive ventricular late potential (VLP) and to discuss the effect of medicine on high risk VA. METHODS: 30 A total of 128 patients (78 males and 50 females) with VA of positive VLP were randomly divided into 3 groups. Groups A and B were given metoprolol and propafenone respectively, group C was given vitamin C as placebo. Twenty-four hours dynamic electrocardiogram and VLP were examined before treatment and 4 weeks after treatment. RESULTS: Propafenone could effectively control VA but could not reverse positive VLP to negative meanwhile it had proarrhythmia effect (2/40), metoprolol could effectively control VA (38/46) and reverse positive VLP to negative (39/46) with no obvious side effects. The dosage from 50 to 100 mg/day made no difference. VA and VLP had no significant changes in group C. CONCLUSIONS: Metoprolol is superior to other medicine for VA of positive VLP when the patients have no contraindication of preceptor blocking agents.

Adult↗
PubMed1996

Dynamic contributions to the DNA binding entropy of the EcoRI and EcoRV restriction endonucleases.

Molecular Dynamics simulations on DNA-EcoRI and DNA-EcoRV complexes suggest that the DNA within these complexes is significantly more ordered than free DNA. Similarly, both the protein and the DNA are more ordered in the specific (cognate) DNA-EcoRV complex than they are in the non-cognate DNA-protein complex, consistent with recently proposed analogies between protein folding and sequence-specific DNA-protein recognition. Analysis of the trajectories shows that the net entropy gain upon specific binding to be the result of opposing contributions. Solvent release, which increases entropy versus configurational terms (as measured by the magnitude of the atomic fluctuations), and collective terms from tight coupling between the motions of the protein and the DNA.

Computer Simulation↗
PubMed1996

Immunosuppression induces transcription of murine cytomegalovirus glycoprotein H in the eye and at non-ocular sites.

In these studies, DNA PCR was used to identify sites of murine cytomegalovirus (MCMV) latency after inoculation of virus into the supraciliary space of the eye. Reverse transcription (RT) PCR for an immediate early gene and a late gene was used to identify putative sites of virus reactivation after methylprednisolone (steroid)-induced immunosuppression. Ten weeks after inoculation of 5 x 10(2) PFU of MCMV, BALB/c mice were immunosuppressed by intramuscular injection of steroid. Control mice were infected but not immunosuppressed. Two weeks after initiation of immunosuppression, mice were sacrificed. DNA and RNA extracted from homogenized tissues were amplified for immediate early gene 1 (IE1) and late gene, glycoprotein H (gH), DNA and mRNA by PCR and RT-PCR, respectively. Replicating virus was detected in homogenized ocular and non-ocular tissues by plaque assay. In the latently infected PBS-treated control group, viral DNA was detected in the inoculated eye and in several non-ocular tissues; IE1 mRNA was found in most of the DNA-positive tissues, while gH mRNA was amplified only in a few of the MCMV DNA-positive tissues from a single mouse. After immunosuppression, viral DNA and IE1 mRNA were detected at a higher frequency in various tissues of steroid-treated mice. gH mRNA was detected in a significantly higher number of the inoculated eyes, salivary glands and other non-ocular tissues of steroid-treated mice. After immunosuppression, low titers of infectious virus were recovered from the salivary glands of steroid-treated mice, but infectious virus was not recovered from the inoculated eye of either steroid-treated of non-immunosuppressed mice. The DNA PCR results suggest that after inoculation of 5 x 10(2) PFU of MCMV into the supraciliary space of euthymic BALB/c mice, virus becomes latent in the inoculated eye, salivary gland and other extraocular tissues. The RT-PCR results suggest that latent MCMV can be reactivated in multiple tissues by immunosuppression.

Animals↗
PubMed1996

Review of the impact on the activation of the human immunodeficiency virus type 1 of ultraviolet light.

Acquired immune deficiency syndrome is a devastating disease with a high mortality rate and the failure of adequate therapy and vaccine stands in sharp contrast to the ultimate progress made in the biomedical sciences. We review the damaging effects of ultraviolet rays on the activation of the human immunodeficiency virus type-1, and theorize that human immunodeficiency virus type-1 positive individuals should minimize their exposures to prolonged and unnecessary ultraviolet radiations such as sunbaths, phototherapy or cosmetic treatments based on a risk-benefit analysis as more epidemiological studies are investigated.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Tandem genes encode cell-surface polypeptides SspA and SspB which mediate adhesion of the oral bacterium Streptococcus gordonii to human and bacterial receptors.

The highly conserved antigen I/II family of polypeptides produced by oral streptococci are believed to be colonization determinants and may mediate adhesion of bacterial cells to salivary glycoproteins absorbed to cells and tissues in the human oral cavity. Streptococcus gordonii is shown to express, on the cell surface, two antigen I/II polypeptides designated SspA and SspB (formerly Ssp-5) that are the products of tandemly arranged chromosomal genes. The structure and arrangement of these genes is similar in two independently isolated strains, DL1 and M5, of S. gordonii. The mature polypeptide sequences of M5 SspA (1539 amino acid (aa) residues) and SspB (1462 aa residues) are almost wholly conserved (98% identical) in the C-terminal regions (from residues 796 in SspA and 719 in SspB, to the respective C-termini), well-conserved (84%) at the N-terminal regions (residues 1-429), and divergent (only 27% identical residues) within the intervening central regions. Insertional inactivation of the sspA gene in S. gordonii DL1 resulted in reduced binding of cells to salivary agglutinin glycoprotein (SAG), human erythrocytes, and to the oral bacterium Actinomyces naeslundii. Further reductions in streptococcal cell adhesion to SAG and to two strains of A. naeslundii were observed when both sspA and sspB genes were inactivated. The results suggest that both SspA and SspB polypeptides are involved in adhesion of S. gordonii cells to human and bacterial receptors.

Actinomyces↗
PubMed1996

Spread of murine cytomegalovirus to inner ocular structures following disruption of the blood-retina barrier in immunosuppressed BALB/c mice.

PURPOSE: The aims of this study were to determine whether disruption of the blood-retina barrier (BRB) increases spread of murine cytomegalovirus (MCMV) to the eye after intraperitoneal inoculation and whether systemic immunosuppression influences the location of MCMV in the ocular compartment. METHODS: The BRB of the left eye of normal and immunosuppressed mice was disrupted by supraciliary inoculation of tissue culture medium followed 2 hours later by intraperitoneal injection of MCMV. Plaque assay of homogenized ocular tissue was used to determine the frequency of virus-positive eyes and the titer of virus in the eyes. Beta-galactosidase staining of frozen sections was used to locate virus in the eyes. RESULTS: In nonimmunosuppressed mice, the frequency of virus isolation, as well as the titer of virus, were significantly higher in eyes in which the BRB had been disrupted. Although the frequency of virus isolation was the same in both eyes of immunosuppressed mice, the titer of virus was significantly higher in the eye in which the BRB had been disrupted. The most striking result was that the location of virus was different in the nondisrupted eyes of immunosuppressed mice than it was in the disrupted eyes of immunosuppressed mice. In the former, virus was seen only in the outer ocular structures (conjunctiva, sclera, lacrimal gland), whereas in the latter, virus was observed in the retina and anterior segment (iris, ciliary body) as well as the outer ocular structures. CONCLUSIONS: The results of these studies suggest that ocular damage followed by increased spread of virus to and within the eye during systemic infection with CMV may be one mechanism by which development of CMV retinitis is facilitated in patients with acquired immune deficiency syndrome.

Animals↗
PubMed1995

Clinical application of modified Anyang type 2 esophageal intubation instrument--a new esophageal intubation method.

The preliminary experience in the clinical use of Anyang Type 2 esophageal intubation instrument, designed by ourselves, in 11 patients with severe esophageal obstruction due to advanced carcinoma of the esophageal was reported. The diagnosis of all 11 cases was confirmed by barium-meal roentgenography. After intubation, all the patients could take liquid or soft diet by mouth. There was no operative mortality and the patients survived 2 to 14 months (mean 5.7 months). All of them could take food by mouth before death. The clinical application proved that the intubation has been a safe and suitable management.

Adult↗
PubMed1995

[Application of transcranial color Doppler flow imaging in the carotid cavernous sinus fistulae].

Transcranial color Doppler flow imaging (TCCDFI) allows for simultaneous two-dimensional structural imaging and Doppler evaluation of blood flow through intact skull. With this technique, we evaluated 10 patients with carotid cavernous sinus fistulae (CCSF) and 35 normal volunteers. Each of them was confirmed by angiography. TCCDFI showed that patients with CCSF had typical signs in the affected part. The cavernous sinus had mosaic color shade. Pulse-Doppler showed disorderly polydirection vortex blood flow spectra in the mosaic color shade associated with murmur. Two-dimensional sonography and color Doppler imaging demonstrated a dilated superior ophthalmic vein (SOV) with arterialized blood flow. The Vmax of MCA and ACA in the affected side were lower than the healthy and normal side. The RI was lower than that of the healthy side and PCA of both sides was lower than that in normal volunteers. Two patients were examined after tubolization. Mosaic color shade disappeared and SOV returned to normal venous flow in patients completely occluded. Mosaic color shade reduced and SOV still aterialized blood flow in partly occluded patients. This technique helps to confirm the clinical diagnosis and to track the hemodynamics of CCSF patients and evaluate the effect of therapy.

Adolescent↗
PubMed1994

Purification and characterization of multiple forms of the pineapple-stem-derived cysteine proteinases ananain and comosain.

A mixture of ananain (EC 3.4.22.31) and comosain purified from crude pineapple stem extract was found to contain numerous closely related enzyme forms. Chromatographic separation of the major enzyme forms was achieved after treatment of the mixture with thiol-modifying reagents: reversible modification with 2-hydroxyethyl disulphide provided enzyme for kinetic studies, and irreversible alkylation with bromotrifluoroacetone or iodoacetamide gave enzyme for structural analyses by 19F-n.m.r. and electrospray mass spectrometry respectively. Structural and kinetic analyses revealed comosain to be closely related to stem bromelain (EC 3.4.22.32), whereas ananain differed markedly from both comosain and stem bromelain. Nevertheless, differences were seen between comosain and stem bromelain in amino acid composition and kinetic specificity towards the epoxide inhibitor E-64. Differences between five isolatable alternative forms of ananain were characterized by amidolytic activity, thiol stoichiometry and accurate mass determinations. Three of the enzyme forms displayed ananain-like amidolytic activity, whereas the other two forms were inactive. Thiol-stoichiometry determinations revealed that the active enzyme forms contained one free thiol, whereas the inactive forms lacked the reactive thiol required for enzyme activity. M.s. provided direct evidence for oxidation of the active-site thiol to the corresponding sulphinic acid.

Amino Acid Sequence↗
PubMed1994

Protease substrate specificity mapping using membrane-bound peptides.

A method is described for assessing the substrate specificity of proteases by screening for proteolytic activity against large numbers of peptides. All 400 possible peptides derived from the 20 common amino acids were synthesized on small membrane disks in the arrangement FTC-spacer-amino acid P1-amino acid P'1-spacer-membrane, where FTC is a chromophoric group. The disks are incubated simultaneously with the protease, resulting in cleavage of the peptide between the P1 and P'1 amino acids, and the absorbance of the released chromophore is measured as a function of time. As demonstrated for chymotrypsin and papain, plots of the resulting data present a perspective view of the amino acid preferences on both sides of the scissile bond. This technique is fast, requires relatively little enzyme, and can be extended to the systematic screening of longer peptides, including analogs with unnatural amino acids. It has potential use for characterizing the specificity of proteases, assessing the results of site-specific mutagenesis, and searching for optimal substrates and inhibitors.

Amino Acid Sequence↗
PubMed1994

Molecular dynamics simulations suggest that the Eco RI kink is an example of molecular strain.

The energy surface in the vicinity of the "Eco RI kink" was investigated by conducting both in vacuo molecular dynamics simulations as well as a simulation with explicit solvent. The in vacuo simulations used the "all atom" AMBER 3.0 force field with a distant dependent dielectric function and "hydrated" counter ions while the simulation with explicit solvent used the AMBER 4.0 force field, fully charged phosphates and counter ions and a dielectric constant of 1.0. The thrust of the simulations was to discriminate between two models of the energy surface of the deformed DNA as found in the recognition complex with Eco RI endonuclease. In the intrinsic model, the kinked DNA is a local minimum of the energy surface intrinsic to the DNA itself while in the strained model there is no significant energy barrier separating kinked and regular B-DNA. The two models have significant implications for theories of indirect recognition of DNA based on sequence-dependent deformability. The simulations suggest that the Eco RI-kinked structure is an example of molecular strain because it is not near a minimum of any of the potential energy functions examined. The simulations leave the question of an energy barrier somewhat open and raise the possibility that the Eco RI kink is at (or near) a point of dynamic instability of the energy surface (either a true maximum or a saddle point).

Base Sequence↗