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Biomedical subjects

H Yan

Publications and source records attributed to H Yan.

At least 127 records · Page 7Linked to original sources
PubMed1999

[Analysis of the clinical characteristics and the pathology of large cell lung cancer].

OBJECTIVE: To study the clinical characteristics and the pathology of large cell lung cancer (LCLC). METHODS: Comparing the microscopic and immunohistochemical findings with clinical data by analyzing 54 cases of surgically treated LCLC from 1978 to 1997. RESULTS: There were 6 cases of clear cell carcinoma and one case of giant cell carcinoma in 54 cases. Male:female was 5:1(45/9). LCLC accounted for 1.28% of all surgically treated lung cancers. The average survival time was 23 months. The positive rate of P53 protein expression was 65%(13/20). The positive rate of PCNA staining was 100%(20/20). CONCLUSIONS: LCLC may be divided into squamous type, adenomatous type, neuroendocrine type and undifferentiated type.

Adult↗
PubMed1999

[Expression and distribution of bFGF mRNA in lung tissue of rat with chronic pulmonary hypertension].

To evaluate the role of basic fibroblast growth factor (bFGF) in the development of hypoxic pulmonary hypertension, 30 wistarmale rats were divided into hypoxic group and control group. Rat models with chronic hypoxia induced pulmonary hypertension were established. The pulmonary hemodynamics was measured and the concentration of bFGF in rat lung tissue was determined quantitatively by enzyme-linked immunosorbent assay (ELISA). Expression and distribution of bFGF messenger ribonucleic acid (mRNA) in rat lung was observed by in situ hybridization using digoxigenin-labeled oligonucleotide probe. The result showed the mean pulmonary artery pressure and the concentration of bFGF in rat lung tissue were 3.96 +/- 0.47 kPa, 18.06 +/- 2.97 pg/ml in rats exposed to hypoxia for 3 weeks, respectively; both were significantly higher than those in control group (P < 0.01, P < 0.001 respectively); expression of bFGF mRNA in the wall of pulmonary arterioles in rats exposed to hypoxia was stronger than that of control group. bFGF mRNA increased obviously in endothial cells, smooth muscle and advential tissue of pulmonary arterioles. These suggest that bFGF takes part in reconstruction of pulmonary arterioles wall in chronic hypoxic pulmonary hypertension, and the main mechanism of bFGF in modulating the structural remodeling of pulmonary arterioles may be autocrine and paracrine.

Animals↗
PubMed1999

[Determination of oleanolic acid and ursolic acid in spica Prunellae by derivative GC method].

OBJECTIVE: To develop a GC method to determine the oleanolic acid and ursolic acid in Spica Prunellae. METHOD: Before GC analysis, the sample was derivatized with CH2N2 solution. The GC conditions were as follows: comumn-10% SE-30(2m x 3mm) and column temperature -270 degrees C. RESULT: The two constituents were well separated and had good linearity in the range of 0.0025-0.4000 mg/ml. The average recoveries and RSD of oleanolic acid were 93.53% and 3.5%, 94.18% and 3.0% respectively. CONCLUSION: The method is good for determining oleanolic acid and ursolic acid in Chinese medicines.

Chromatography, Gas↗
PubMed1999

[Immunogenicity and immunoprotection of a leptospiral DNA vaccine].

Leptospirosis is one of the most widespread zoonosis. Immunization of NZW rabbit with plasmid DNA constructs encoding leptospiral endoflagellin can induce specific antibody response in the animal. The vector, VR1012 consists of a pUC18 backbone with the cytomegalovirus (CMV) IE1 enhancer, promoter, and intron A transcription regulatory elements and the BGH polyadenylation sequences driving the expression of leptospiral endoflagellar gene, flaB2. In this study, a pair of oligonucleotide primers were designed to amplify the endoflagellar of L. interrogans serovar lai. An approximately 840 bp fragment was generated with PCR and inserted into expressed plasmid vector, VR1012, after the fragment of VR1012 were digested respectively with EcoRV and Sall. A recombinant plasmid (designated VR1012 + flaB2) was obtained. Plasmid encoding leptospiral endoflagellin was injected into quadriceps of NZW rabbits. This resulted in the generation of specific leptospiral antibody with very high ELISA titer. Immunoprotection was performed in guinea pigs. The group "VR1012 + flaB2" had higher survival rate, compared with the group "VR1012 only" (control) and the group "Normal Saline only" (control). The result suggests that the technique of DNA injection should have an advantage over certain previous vaccine technologies.

Animals↗
PubMed1999

[Changes and clinical significance of serum thyroxine level in patients with congestive heart failure].

In order to explore the relationship between congestive heart failure (CHF) and serum thyroxine, we assayed serum thyroxine level in 52 patients with CHF and 28 normal persons by means of radioimmunoassay (RIA). The results showed that triiodothyronine reduced and reverse triiodothyronine elevated significantly in the patients compared with the normal (P < 0.05). The more severe heart failure developed, the more obvious changes of the hormones were observed. The results suggest that the alterations of serum thyroid level may be used as an index of the severity of heart failure.

Adult↗
PubMed1999

[Molecular cloning and sequencing of outer capsid protein gene of rice dwarf virus and its expression in Escherichia coli].

The S2 full-length cDNA of rice dwarf phytoreovirus which enocodes the viral outer capsid protein was cloned and its complete nucleotide sequence was determined. The results showed that S2 is 3512 bp long with a large open reading frame which encodes a protein of 1116 amino acids. It shares 94.6% and 95.4% identity with RDV of Japanese H isolate in terms of nucleotide and amino acid sequences, respectively, and it also shows some homology with VP2 of rotavirus at the level of amino acid sequence. The search of deduced RDV S2 amino acid sequence in Blast network found that there were 4 leucine-rich motifs in P2 protein, and ten amino acids within the hydrophibic region at amino-terminus could form an alpha-helix. Predicted secondary structure of S2 cDNA indicated that a hairpin and a stem loop are present in the 5'-end within 50 bp, and a stem loop in the 3'-end within 50 bp. RDV S2 partial and full-length sequences were then cloned into expression vector pET-11d & pTrcHisC. SDS-PAGE and Western blot proved that amino- and carborn-termini of P2 were successfully expressed in E. coli.

Amino Acid Sequence↗
PubMed1999

[Analyses of central serous chorioretinopathy from indocyanine green angiography].

PURPOSE: To compare and analyse the characters of Indocyanine Green Angiography (ICGA) and Fundus Fluorescein Angiography (FFA) in Central Serous Chorioretinopathy (CSCR) and explore its pathological significance. METHOD: 35 cases of CSCR were examed with Heidelberg Retina Angiography. Simultaneous images of ICGA and FFA were analysed. RESULTS: Among the 35 cases, 29(83%) revealed more lesions in ICGA than in FFA. The lesions appeared in FFA were all associated with ICGA changes. CONCLUSION: The increasing of choroid hyperpermeability is an early change, which causes the overlying RPE dysfunction and structural damage. Some points related to the laser and medical treatment to CSCR were also discussed.

Angiography↗
PubMed1999

[Detection of viral markers in liver tissue dually infected with hepatitis B and C viruses by double labelling].

OBJECTIVE: To study the distribution and mutual relation of HBV and HCV in dually infected liver tissue. METHODS: Detected HBV and HCV nucleic acids and their antigens by immunohistochemistry and in situ hybridization, the cases with HBcAg and HCV RNA positive were tested further on single section by double labeling. RESULTS: On the section tested by double labeling we could see that positive hepatocytes infected with HBV or HCV were mostly present in different liver lobules, even if the two viruses were seen in the same lobule, most of them were not seen within a single cell. CONCLUSIONS: In most of hepatocytes, there was no direct interference or suppression of each other in the liver tissue dually infected with HBV and HCV. Double labeling method is useful to analyze the coinfection of two viruses in the same tissue.

DNA, Viral↗
PubMed1999

Comparison of bone mass in forearm, lumbar vertebra and hip by single and/or dual energy X-ray absorptiometry.

OBJECTIVE: Bone mineral density (BMD) was measured in normal Chinese women with single X-ray absorptiometry (SXA) and dual energy X-ray absorptiometry (DEXA). These two methods were compared to evaluate the sensitivity in reflecting bone loss. METHODS: Measurements were performed in 300 women aged 20 to approximately 79 (5 for each age). The 8mm distal, 1/4 distal, ultra distal site of the nondominant forearm were measured with SXA; the AP spine (L2-4), right femoral neck (Neck), Ward's triangle (Ward) and trochantor (Troch) were measured with DEXA. Ten women had 5 repeated measurements to evaluate the reproducibility of the equipments. RESULTS: The BMD peak for Neck and Ward was found between age 20 to approximately 29, for ultra distal and L2-4 at age 30 to approximately 39, for 8mm distal, 1/4 distal and Troch at age 40 to approximately 49. After reaching the peak values, BMD at all sites decreased with increasing age. The highest rate of yearly loss of BMD was at 8mm distal. Results of measurement showed significant correlation between SXA and DEXA. Comparing with premenopausal women, the bone loss rate in postmenopausal women was faster and highest up to 11 to approximately 15 years and the highest rate was at the Ward. CONCLUSION: The present study gives the normal values of BMD at seven sites for normal Chinese women. The ages of BMD peak were different at seven sites. The yearly loss of BMD was highest at 8mm distal, it seemed to be the sensitive region for bone loss with age. The postmenopausal women had highly significantly loss bone mass than the premenopausal women. Comparing with premenopause, postmenopause BMD for Ward's triangle with DEXA seemed to be most sensitive to the effect of menopause.

Absorptiometry, Photon↗
PubMed1998

NMR solution structure of type II human cellular retinoic acid binding protein: implications for ligand binding.

The structure of human apo-cellular retinoic acid binding protein II (apo-CRABPII) in solution at pH 7.3 has been determined by NMR spectroscopy. The sequential assignments of the 1H, 13C, and 15N resonances of apo-CRABPII were established by multinuclear, multidimensional NMR spectroscopy. The solution structure of apo-CRABPII was derived from 2382 experimental NMR restraints using a hybrid distance geometry-simulated annealing protocol. The root-mean-square deviation of the ensemble of 25 refined conformers that represent the structure from the mean coordinate set derived from them was 0.54 +/- 0.18 and 0.92 +/- 0.20 A for the backbone atoms and all heavy atoms, respectively, of all residues except Ala32-Pro39 and Thr57-Glu62, which are in disordered regions. The solution structure of apo-CRABPII is similar to the crystal structure of holo-CRABPII [Kleywegt, G. J., Bergfors, T., Senn, H., Le Motte, P., Gsell, B., Shudo, K., and Jones, T. A. (1994) Structure 2, 1241-1258] except the ligand entrance, which is sufficiently enlarged in the apoprotein to be readily accessible to retinoic acid. The enlargement of the ligand entrance of apo-CRABPII relative to that of holo-CRABPII is due mainly to a concerted conformational change in three structural elements, namely, the second helix, the betaC-betaD loop, and the betaE-betaF loop. Furthermore, the ligand-binding pocket of apo-CRABPII showed evidence of dynamic disorder; among the 21 residues that constitute this pocket, 16 residues had weak or no detectable cross-peaks in the two-dimensional 1H-15N HSQC spectrum recorded under conditions of minimal water saturation or dephasing. Apo-CRABPII is largely monomeric in solution, with no evidence for the dimeric structure shown in the crystal structure of apo-CRABPI which was suggested to be a prerequisite for ligand entry [Thompson, J. R., Bratt, J. M., and Banaszak, L. J. (1995) J. Mol. Biol. 252, 433-446]. Thus, the widening of the ligand entrance required for entry of retinoic acid appears to be a property of monomeric apo-CRABPII.

Crystallization↗
PubMed1998

NMR study suggests a major role for Arg111 in maintaining the structure and dynamical properties of type II human cellular retinoic acid binding protein.

The solution structure of a site-directed mutant of type-II human cellular retinoic acid binding protein (CRABPII) with Arg111 replaced by methionine (R111M) has been determined by NMR spectroscopy. The sequential assignments of the 1H and 15N resonances of apo-R111M were established by multinuclear multidimensional NMR. The solution structure was calculated from 2302 distance restraints and 77 phi dihedral restraints derived from the NMR data. The root-mean-square deviation of the ensemble of 28 refined conformers that represent the structure from the mean coordinate set derived from them was 0.54 +/- 0.26 and 0.98 +/- 0.23 A for the backbone atoms and all heavy atoms, respectively. The solution structure of apo-R111M is similar to that of wild-type apo-CRABPII. However, there are significant conformational differences between the two proteins, localized mainly to three segments (Leu19-Ala36, Glu73-Cys81, and Leu99-Pro105) clustered around the ligand entrance more than 17 A away from the point mutation. In apo-R111M, all the three segments move toward the center of the ligand entrance so that the opening of the ligand-binding pocket in apo-R111M is much smaller than that in wild-type apo-CRABPII. Furthermore, the ligand-binding pocket of apo-R111M, especially the ligand entrance, is much less flexible than that of apo-CRABPII. Surprisingly, apo-R111M is more similar to holo-CRABPII than to apo-CRABPII in both structure and dynamical properties. The conformational and dynamical changes caused by the mutation are similar to those induced by binding of RA, although the magnitudes of the changes caused by the mutation are smaller than those induced by binding of RA. The results suggest that Arg111 plays a critical role in determining the structure and dynamical properties of CRABPII.

Amino Acid Sequence↗
PubMed1998

Calculation of concentrations of equilibrium components in an in vitro activity test of vancomycin antibiotics and the possible mode of action.

The vancomycin group of antibiotics is considered to act by binding the bacterial cell wall mucopeptide precursor terminating in -L-Lys-D-Ala-D-Ala. The dimerization of these antibiotics is also believed to play a role in the action. In this paper, we analyzed the equilibria in the in vitro antibacterial activity test of the vancomycin antibiotics both with and without the cell wall precursor analogue di-acetyl-L-Lys-D-Ala-D-Ala (DALAA). Based on the equilibria and concentration balance, we obtained 10 equations (seven quadratic equations and three linear equations) containing 10 equilibrium concentrations which relate to the antibiotic, cell wall precursor and DALAA. A computer program was written to solve these equations from known dimerization constant and the binding constants (both monomer and dimer) with DALAA of the antibiotic. The concentrations in the test for vancomycin and eremomycin were obtained. The antibiotic activity of these antibiotics may be quantitatively correlated with their dimerization constants and the binding constants through the calculation. By analyzing the calculated results, we concluded that the cell wall-bound dimer may be the major contributor to the antibiotic activity in the case of eremomycin, while the cell wall-bound monomer is possibly the determinant for the activity of vancomycin.

Anti-Bacterial Agents↗
PubMed1998

Crystal structure of apo-cellular retinoic acid-binding protein type II (R111M) suggests a mechanism of ligand entry.

The crystal structure of unliganded mutant R111M of human cellular retinoic acid-binding protein type II (apo-CRABPII (R111M)) has been determined at 2.3 A and refined to a crystallographic R-factor of 0. 18. Although the mutant protein has lower affinity for all-trans-retinoic acid (RA) than the wild-type, it is properly folded, and its conformation is very similar to the wild-type. apo-CRABPII (R111M) crystallizes in space group P1 with two molecules in the unit cell. The two molecules have high structural similarity except that their alpha2 helices differ strikingly. Analyses of the molecular conformation and crystal packing environment suggest that one of the two molecules assumes a conformation compatible with RA entry. Three structural elements encompassing the opening of the binding pocket exhibit large conformational changes, when compared with holo-CRABPII, which include the alpha2 helix and the betaC-betaD and betaE-betaF hairpin loops. The alpha2 helix is unwound at its N terminus, which appears to be essential for the opening of the RA-binding pocket. Three arginine side-chains (29, 59, and 132) are found with their guanidino groups pointing into the RA-binding pocket. A three-step mechanism of RA entry has been proposed, addressing the opening of the RA entrance, the electrostatic potential that directs entry of RA into the binding pocket, and the intramolecular interactions that stabilize the RA.CRABPII complex via locking the three flexible structural elements when RA is bound.

Apoproteins↗
PubMed1998

Definition of the interferon-alpha receptor-binding domain on the TYK2 kinase.

Interferons and cytokines modulate gene expression via a simple, direct signaling pathway containing receptors, JAK tyrosine kinases, and STAT transcription factors. The interferon-alpha pathway is a model for these cascades. Two receptors, IFNaR1 and IFNaR2, associate exclusively in a constitutive manner with two JAK proteins, TYK2 and JAK1, respectively. Defining the molecular interface between JAK proteins and their receptors is critical to understanding the signaling pathway and may contribute to the development of novel therapeutics. This report defines the IFNaR1 interaction domain on TYK2. In vitro binding studies demonstrate that the amino-terminal half of TYK2, which is approximately 600 amino acids long and contains JAK homology (JH) domains 3-7, comprises the maximal binding domain for IFNaR1. A fragment containing amino acids 171-601 (JH3-6) also binds IFNaR1, but with reduced affinity. Glutathione S-transferase-TYK2 fusion proteins approximating either the JH6 or JH3 domain affinity-precipitate IFNaR1, suggesting that these are major sites of interaction within the larger binding domain. TYK2 amino acids 1-601 act in a dominant manner to inhibit the transcription of an interferon-alpha-dependent reporter gene, presumably by displacing endogenous TYK2 from the receptor. This same fragment inhibits interferon-alpha-dependent tyrosine phosphorylation of TYK2, STAT1, and STAT2.

Binding Sites↗
PubMed1998

Transcriptional activation of the p34cdc2 gene by cdc2 promoter binding factor/nuclear factor-Y in fetal rat ventricular myocytes.

To determine how myocardial terminal differentiation is regulated by cell cycle control genes, we studied cdc2 expression in rat cardiac muscle and found that cdc2 mRNA and protein levels were reduced in neonatal compared with fetal ventricles and became undetectable in juvenile and adult ventricles. To further determine whether cdc2 downregulation is attributed to a decrease in transcription, transient expression assay was performed using the progressively truncated 6.2-, 1.8-, 1.1-, 0.7-, and 0.1-kb human cdc2 5' flanking regions. All five fragments activated reporter expression in fetal myocytes and were significantly less active in neonatal myocytes. The 0.1-kb fragment showed 65% of the activity of the 6.2-kb fragment. A protein binding site that contains an inverted CCAAT box was identified within the 0.1-kb fragment by DNase I footprint assay and named the cdc2 promoter binding factor (CPBF) site. Point mutations within the CPBF site that abolish CPBF binding significantly decreased both 0.1- and 6.2-kb promoter activities. Competition and antibody supershift assays suggested that CPBF was identical or related to the transcription factor, nuclear factor Y (NF-Y). The 0.1-kb promoter activity was suppressed by a dominant-negative NF-Y mutant in fetal myocytes. Taken together, our results demonstrate that cardiac cdc2 expression is downregulated after birth and turned off when the juvenile stage is attained. A 0.1-kb promoter fragment of cdc2 contains major information for both cdc2 transcriptional activation and suppression in fetal and neonatal myocytes, respectively. NF-Y or its related factor plays a critical role in activating the 0.1-kb cdc2 promoter.

Animals↗
PubMed1998

Amyotrophic lateral sclerosis: serum factors enhance spontaneous and evoked transmitter release at the neuromuscular junction.

Sera from 30 patients with sporadic amyotrophic lateral sclerosis (ALS) were tested to determine their effects at the neuromuscular junction. Spontaneous transmitter release was significantly increased, as evidenced by a 151% increase in MEPP frequency, by sera from 16 ALS patients. In addition, 16 patients' sera elevated EEP quantal content by an average of 89%. Eleven sera produced both effects. There was no consistent change in MEPP amplitude or time course, indicating the absence of a humoral effect on postjunctional ACh receptors or endplate membrane function. These results suggest that a portion of the sporadic ALS patient population possess serum factors that can alter presynaptic function of the motor nerve terminal. Evidence from the present experiments indicates that alterations at the neuromuscular junction are a result of a combination of increased Ca2+ influx into the cell and an independent increase in intracellular calcium concentration.

Amyotrophic Lateral Sclerosis↗