Biomedical subjects

R Zhang

Publications and source records attributed to R Zhang.

At least 253 records · Page 14Linked to original sources

PubMed1999

[The outer membrane protein (OMP) patterns of Escherichia coli isolates of predominant O serogroups originated from chichens in different regions in China].

The purpose of this study is to determine the outer membrane protein (OMP) patterns of avian Escherichia coli isolates with predominant serogroups originated from 18 provinces, autonomous regions and municipal cities in China. Total of 204 isolates belonging to O18, O78, O2, O88, O11 and O26 serogroups respectively, were tested. The outer membrane proteins of these isolates were isolated with the improved N-lauroylsarcosine method and analyzed by SDS-PAGE. 4 different OMP patterns were identified with these isolates of predominant serogroups. 3 different OMP patterns with 56 isolates of O18, 4 with 54 isolates of O78, 2 with 28 isolates O2, 1 with 26 isolates of O88, 3 with 22 isolates of O11 and 1 with 18 isolates of O26 respectively, were found. Isolates with OMP pattern 1 were discovered in 6 different serogroups, and OMP-3 pattern was also shared by O18, O78 and O11 serogroups isolates. These results indicated that the OMP patterns of avian pathogenic Escherichia coli isolates of O18, O78, O2, O11 serogroups which were isolated from different regions in China were heterogeneous, and all of O88 and O26 serogroups isolates just belonged to OMP pattern 1. Moreover, the OMP pattern 1 was presented in isolates of six different predominant O serogroups.

Animals↗

PubMed1999

[The isolation and characterization of type 1 pili from pathogenic Escherichia coli of chicken origin].

The pili from pathogenic Escherichia coli isolates 566, 1794 and TK3 of chicken and turkey origin were purified. After mechanic detachment from the bacterial cells, the pili were concentrated by precipitation with ammonium sulfate, dialyzed, and solubilized in buffer containing deoxycholate. The fraction containing the pilus was purified further by ultracentrifugation in a sucrose gradient. After ultracentrifugation, the pili at the density of 1.10 to 1.15 g.cm-3 (between 10%-20% of sucrose gradients) were collected, and the purified pili from strain 566, 1794 and TK3 had an apparent molecular weight of 17,500, 17,000 and 17,000 respectively, which retained their ability to bind the erythrocyte in a mannose-inhibitable fashion. Hyperimmunesera raised in BALB/C mice against the purified pili from strain 1794 reacted positively with type 1 pili from both isolates 566 and TK3 by immuno blot. These results revealed that the three strains either Chinese or north american isolates expressed type 1 pili which had molecular weights from 17,000 to 17,500, and they have common antigenic epitopes.

Animals↗

PubMed1999

[Effects of growth factors and estrogen on the proliferation and prolactin gene expression in anterior pituitary cells of rats].

OBJECTIVE: Detect the effects of exogenous 17 beta-estradiol (E2), epidermal growth factor (EGF), and transforming growth factor beta 1 (TGF beta 1) on the proliferation and prolactin (PRL) gene expression in primary serum-free cultured anterior pituitary cells in vitro. METHODS: Laser scanning confocal microscopy (LSCM) and in situ hybridization in primary serum-free cultures of rat anterior pituitary cells were employed. RESULTS: After 36 hours incubation of the monolayer with E2(10(-8) mol/L) and EGF(10(-8) mol/L), DNA and PRL mRNA contents in the cells were increased significantly (P < 0.001); and when cells were co-incubated with E2 and EGF at the same time, the levels of DNA and PRL mRNA were higher than those treated with E2 or EGF alone (P < 0.01), respectively. TGF beta 1(2 ng/ml) treatment decreased the DNA and PRL mRNA contents significantly (P < 0.001). Its inhibitory effect was reduced at the presence of E2, the DNA and PRL mRNA levels in the cells were higher than those treated with TGF beta 1 alone (P < 0.001), but still lower than E2 alone treatment (P < 0.001). CONCLUSIONS: The results indicate that EGF and TGF beta 1 exerte stimulatory inhibitory effects, on cell proliferation and PRL gene expression in anterior pituitary cells of rats in both basal and E2-induced conditions. EGF and TGF beta 1 may be involoved in the regulation of proliferation and PRL gene expression in anterior pituitary cells in vivo; and also may be correlated with prolactin-secreting tumors formation induced by E2.

Animals↗

PubMed1999

[The polymerization of C60/C70 in air at high temperature].

C60(C70 contained) was sealed in air and heated for 10 minutes at high temperature (850-900 degrees C). It was found from absorption spectrum analysis and SEM observation that the C60(C70) produced polymerization under the action of nitrogen and oxygen.

English Abstract↗

PubMed1998

Application of analytical and preparative high-speed counter-current chromatography for separation of alkaloids from Coptis chinensis Franch.

Analytical high-speed counter-current chromatography (HSCCC) was used for the systematic selection and optimization of the two-phase solvent system to separate alkaloids from Coptis chinensis Franch. The optimum solvent system thus obtained led to the successful separation of alkaloids from C. chinensis Franch by preparative HSCCC. One batch separation yielded four pure alkaloids, including palmatine, berberine, epiberberine and coptisine from the crude alkaloid extract.

Alkaloids↗

PubMed1998

Biphenylsulfonamide endothelin antagonists: structure-activity relationships of a series of mono- and disubstituted analogues and pharmacology of the orally active endothelin antagonist 2'-amino-N- (3,4-dimethyl-5-isoxazolyl)-4'-(2-methylpropyl)[1, 1'-biphenyl]-2-sulfonamide (BMS-187308).

Substitution at the ortho position of N-(3,4-dimethyl-5-isoxazolyl) benzenesulfonamide led to the identification of the biphenylsulfonamides as a novel series of endothelin-A (ETA) selective antagonists. Appropriate substitutions on the pendant phenyl ring led to improved binding as well as functional activity. A hydrophobic group such as isobutyl or isopropoxyl was found to be optimal at the 4'-position. Introduction of an amino group at the 2'-position also led to improved analogues. Combination of the optimal 4'-isobutyl substituent with the 2'-amino function afforded an analogue (20, BMS-187308) with improved ETA binding affinity and functional activity. Compound 20 also has good oral activity in inhibiting the pressor effect caused by an ET-1 infusion in rats. Doses of 10 and 30 micromol/kg iv 20 attenuated the pressor responses due to the administration of exogenous ET-1 to conscious monkeys, indicating that the compound inhibits the in vivo activity of endothelin-1 in nonhuman primates.

Administration, Oral↗

PubMed1998

A new quantitative criterion to distinguish between alpha/beta and alpha+beta proteins (domains).

According to the statistical analysis, it is shown that the differences of the content of alpha-helix and beta-strand between alpha/beta and alpha+beta proteins are of statistical significance. Based on the secondary structure content and the percentage of parallel or anti-parallel strands, any mixed alphabeta protein can be represented by a point in a three-dimensional prism. The distribution of the mapping points for 79 mixed alphabeta proteins (domains), of which 26 are class alpha/beta and 53 are class alpha+beta, shows that the two kinds of points are situated at distinct regions roughly. A new quantitative criterion based on the Fisher discriminant algorithm is proposed to distinguish between the alpha/beta and alpha+beta proteins (domains). Of the 79 proteins 77 are correctly classified (97.5%). As a stringent cross-validation test, the jackknife test shows that of the 79 proteins 77 are correctly classified. The jackknife test accuracy is still 97.5%. These figures indicate the self-consistence and the extrapolating effectiveness of the new quantitative criterion. Applying the new criterion to reclassify the alpha/beta and alpha+beta proteins (domains) in SCOP is also discussed. It is hoped that the new quantitative criterion will be useful for the development of protein classification databases.

Algorithms↗

PubMed1998

Cellular terrain surrounding sympathetic nerve pathways in the rat orbit: comparisons of orbital connective tissue and smooth muscle cell phenotypes.

Sympathetic axons are abundant within some orbital tissues but are absent from others. This study investigated cellular phenotypes of tissues containing sympathetic nerves en passage and compared these with phenotypes in regions devoid of sympathetic nerves and with smooth muscle targets. Two primary orbital smooth muscle targets, the tarsal muscle and orbital muscle, contained many synaptophysin-immunoreactive nerves. Target cells had ultrastructural features typical of smooth muscle and were immunoreactive for alpha-smooth muscle actin, smooth muscle myosin heavy chain, desmin, vinculin, and laminin, but not non-muscle myosin, vimentin, fibronectin, or type IV collagen; nerve growth factor (NGF) mRNA was detected by reverse transcription-polymerase chain reaction. Periorbital sheath devoid of sympathetic nerves contained elongated fibroblasts that were immunoreactive for vimentin, non-muscle myosin, and fibronectin, but not for alpha-smooth muscle actin, smooth muscle myosin heavy chain, vinculin, desmin, laminin, or type IV collagen, and did not express NGF mRNA. Regions of periorbital sheath containing sympathetic nerves had few synaptophysin-immunoreactive varicosities. Cells in this region contained myofilaments, ribosomes, and rough endoplasmic reticulum and were larger than tarsal muscle cells. They expressed NGF mRNA and showed a unique immunophenotype, reacting for vimentin, alpha-smooth muscle actin and myosin heavy chain, desmin, vinculin, laminin, and type IV collagen. This phenotype reflects both fibroblast and smooth muscle features similar to myofibroblasts or transdifferentiated smooth muscle described in other tissues. The spatial association between these cells and sympathetic nerves suggests that they may be involved in axon guidance or maintenance.

Animals↗

PubMed1998

Comparison of murine Supt4h and a nearly identical expressed, processed gene: evidence of sequence conservation through gene conversion extending into the untranslated regions.

We show herein the transcription of a processed gene that originated from a spliced transcript. Recently, we isolated the human and murine homologues of the yeast chromatin protein, SPT4. The Supt4h gene is spliced normally from five exons encoded by chromosome 11. Here we show that a related sequence on chromosome 10 encodes Supt4h2, a processed intronless gene (with a polyA tail and a tandemly-duplicated 13 bp insertion site in the genome) with a different 5' control region. Both the spliced gene, Supt4h , and the processed gene, Supt4h2 , are expressed in each of four tissues we examined. Supt4h2 encodes a 117 amino acid protein nearly identical to the Supt4h gene product with only one amino acid difference, indicating extreme conservation of this expressed processed gene with the spliced gene over evolutionary time. This illustrates another potential complexity of the mammalian genome, i.e. the use of a processed gene under the control of a different promoter region than the spliced gene.

Animals↗

PubMed1998

Presynaptic adrenergic facilitation of parasympathetic neurotransmission in sympathectomized rat smooth muscle.

1. Parasympathetic innervation of rat eyelid tarsal smooth muscle normally inhibits sympathetic neurotransmission prejunctionally without significant direct postjunctional effects. Following surgical sympathectomy, parasympathetic stimulation elicits smooth muscle contraction. This study examined the relative contributions of cholinergic and adrenergic mechanisms mediating these contractions. 2. Electrical stimulation of the superior salivatory nucleus, which activates tarsal muscle parasympathetic nerves, elicited large contractions at 2 days postsympathectomy, which were abolished by atropine and were decreased by 65 % by alpha1-adrenoceptor blockade or spinal cord transection. 3. Contractions in response to direct cholinergic stimulation by bethanechol at 2 days postsympathectomy were increased following spinal cord transection (C2) and suppressed by the alpha1-adrenoceptor agonist phenylephrine, indicating that adrenoceptors on smooth muscle attenuate cholinergic contractions. However, phenylephrine infusion enhanced contractile responses to parasympathetic stimulation. 4. Reverse transcription-polymerase chain reaction revealed alpha1D-adrenoceptor mRNA within pterygopalatine ganglia. 5. At 5 weeks and 14 months postsympathectomy, adrenergic facilitation was significantly less than at 2 days, whereas prazosin-insensitive muscarinic contraction was increased. 6. We conclude that degeneration of sympathetic innervation is followed rapidly by adrenoceptor-mediated prejunctional enhancement of parasympathetic nerve-smooth muscle neurotransmission, which occurs prior to neuroeffector junction formation as determined previously by electron microscopy. Subsequently, noradrenergic enhancement is diminished as cholinergic neurotransmission becomes established.

Animals↗

PubMed1998

p53 gene mutations in rectal cancer associated with schistosomiasis japonica in Chinese patients.

Mutations in p53 tumor suppressor gene were examined in 44 Chinese patients with rectal cancer, including 22 cases with advanced schistosomiasis japonica and 22 cases without schistosomiasis. In schistosomal rectal cancer (SRC), 13 mutations were found in 10 cases, which included 11 base-pair substitutions and two deletions. Of 11 base substitutions, nine were transitions and two were transversions and seven of them were located at CpG dinucleotides. In non-schistosomal rectal cancer (NSRC), 13 mutations were found in nine cases, all of which were base-pair substitutions. Of 13 substitutions, 10 were transitions and three were transversions and three of them were located at CpG dinucleotides. The proportion of base-pair substitutions at CpG dinucleotides was higher in SRC patients than in NSRC patients, although this was not statistically significant (P = 0.054). Point mutation was frequent at codon 248 in SRC. A higher frequency of arginine missense mutations was observed in SRC than in NSRC. These observations suggest that the mutations in SRC are the result of genotoxic agents produced endogenously through the course of schistosomiasis japonica.

Aged↗

PubMed1998

A novel approach to distinguish between intron-containing and intronless genes based on the format of Z curves.

A novel method to distinguish between intron-containing and intronless DNA sequences has been proposed, based on different statistic behaviors between them. In this method, DNA sequences are first represented as Z curves. Three exponents alpha, beta and gamma for each given sequence are calculated based on the format of the Z curve for the DNA sequence. A three-dimensional space is spanned by the three exponents. Each DNA sequence may be represented by a point in this space. One hundred intronless and intron-containing genes, respectively, were selected randomly from the GenBank or EMBL database. It is shown that the 200 points are roughly distributed in different regions. The best separating plane to separate the two regions is obtained by using Fisher's discriminant algorithm. For any given sequence to be discriminated, calculate three exponents alpha, beta and gamma, corresponding to a point in the three-dimensional space. If the point is situated at the upper region of the separating plane, the sequence is discriminated as an intronless one; otherwise, the sequence is an intron-containing one. A test of the method for the sequences in an independent test set shows that the discriminant accuracy reaches as high as 89.0%.

Animals↗

PubMed1998

Chloramine T-induced structural and biochemical changes in echistatin.

Echistatin is a member of the disintegrin family of peptides and a potent inhibitor of platelet aggregation and cell adhesion. Echistatin binds to integrin alpha(v)beta3 and alpha(IIb)beta3 receptors with high affinity. Binding is mediated by an RGD-containing loop maintained in an appropriate conformation by disulfide bridges. In this study, we have compared the binding characteristics of echistatin iodinated by either lactoperoxidase or chloramine T method. We show that echistatin labeled by lactoperoxidase method binds to integrin alpha(v)beta3 receptor with high affinity and in a non-dissociable manner very similar to native echistatin. In contrast, chloramine T-labeled echistatin can rapidly dissociate from the receptor. We demonstrate that chloramine T reaction results in the addition of an extra oxygen to the methionine residue adjacent to the RGD motif in echistatin. Modeling studies and molecular dynamic simulation studies show that the extra oxygen atom on the methionine residue can form hydrogen bonds with the glycine and aspartic acid residues of the RGD motif. These structural changes in echistatin help explain the changes in the binding characteristics of the molecule following chloramine T reaction.

Chloramines↗

PubMed1998

Asphyxial brain injury--the role of the IGF system.

Transient neural injuries, such as asphyxia, can trigger considerable delayed neuronal death. Inappropriate induction of apoptosis is thought to play an important role in this process. Our studies have shown marked changes in the IGF system in the brain in response to these injuries with an induction of insulin growth factor (IGF)-1 and insulin growth factor binding protein (IGFBP)-2 and IGFBP-3 in glial cells in the region of injury. This suggests that the IGF-1 system may be an endogenous neuroprotective system. Earlier administration of IGF-1 - 2 h after injury reduced the phase of secondary neuronal loss suggesting that IGF-1 may well have therapeutic potential as a neuronal rescue agent. The action of IGF-1 appears to involve binding proteins, transport to the site of injury and the IGF-1 receptor and inhibition of apoptosis, but might also involve generation of GPE which itself appears to be neuroprotective. Together these results indicate considerable potential of these agents to treat stroke, perinatal asphyxia and other forms of acute brain injury.

Animals↗

PubMed1998

Serine protease of hepatitis C virus expressed in insect cells as the NS3/4A complex.

Hepatitis C virus (HCV) protease NS3 and its protein activator NS4A participate in the processing of the viral polyprotein into its constituent nonstructural proteins. The NS3/4A complex is thus an attractive target for antiviral therapy against HCV. We expressed the full-length NS3 and NS4A in insect cells as a soluble fusion protein with an N-terminal polyhistidine tag and purified the two proteins to homogeneity. Cleavage at the junction between HisNS3 and NS4A occurs during expression, producing a noncovalent complex between HisNS3 and NS4A with a subnanomolar dissociation constant. We purified the HisNS3/4A complex by detergent extraction of cell lysate and by metal chelate chromatography. We removed the His tag by thrombin cleavage and then further purified the complex by gel filtration. The purified NS3/4A complex is active in a protease assay using a synthetic peptide substrate derived from the NS5A-NS5B junction, with kcat/K(m) of 3700 (+/- 600) M-1 s-1, an order of magnitude above those previously reported for NS3 expressed by other strategies. This high protease activity implies that the full-length sequences of NS3 and NS4A are required for optimal activity of the NS3 protease domain. We examined the dependence of the NS3/4A protease activity on buffer conditions, temperature, and the presence of detergents. We find that, under most conditions, NS3 protease activity is dependent on the aggregation state of the NS3/4A complex. The monodisperse, soluble form of the NS3/4A complex is associated with the highest protease activity.

Adenosine Triphosphatases↗

PubMed1998

Positively charged dextran resin inhibits trabecular bone repair in the rabbit tibial physis.

Because exposure to positively charged dextran resin (PCDR) inhibits the growth of cultured rat and human bone cells, we tested the hypothesis that PCDR might inhibit bone repair in vivo. Central physeal defects were created by drilling 3.0-mm holes from the proximal tibial plateau into the metaphysis. The defects in left tibiae were packed with neutral resin (control); those in right tibiae were filled with PCDR. At the end of the 1st, 2nd, 3rd, and 10th postoperative weeks, the outcomes were quantitated by documenting the percent trabecular bone volume within the defect. The PCDR-filled defects showed a significant decrease in trabecular bone formation as early as the 2nd week. By the 10th postoperative week, formation of trabeculae had been reduced by nearly 40%. The inhibition conferred by PCDR suggests that the resin could be used as a suppressive interpositional material.

Animals↗

PubMed1998

The expression of P- and E-selectins in three models of middle cerebral artery occlusion.

The expression and localization of P- and E-selectins in rat brain (n=126) were examined using immunohistochemical techniques at various time points after induction of middle cerebral artery (MCA) occlusion in the suture, thrombotic and embolic models of stroke. Expression of P- or E-selectin was not observed in brain tissue of sham operated control rats (n=9). P-selectin immunoreactivity was detected as early as 15 min and decreased to control level at 1 h after the onset of the MCA occlusion in all three models. P-selectin then slightly increased at 2 h and peaked at 6 h after MCA occlusion. E-selectin immunoreactivity was first observed at 2 h and peaked at 6 h and 12 h of after MCA occlusion in all three models. P- and E-selectin immunoreactivity was colocalized with von Willebrand factor immunoreactive microvessels. 90.4+/-2.0% of all vessels expressing P-selectin immunoreactivity were 7.5 to 30.0 micron in diameter; 3.6+/-1.4% were contained in vessels smaller than 7.5 micron, and 6.0+/-1.8% were localized in vessels greater than 30.0 micron in diameter. The percent distribution of E-selectin immunoreactive vessels were 75.9+/-2.1% in vessels 7.5 to 30.0 micron in diameter; 23.6+/-2.2% were in vessels smaller than 7.5 micron, and 0.6+/-0.4% were localized in vessels greater than 30.0 micron in diameter. These findings indicate that the temporal profiles of P- and E-selectin expression are independent of these models of MCA occlusion and are consistent with the time course of selectin mediated leukocyte infiltration after focal cerebral ischemia in the rat.

Analysis of Variance↗

PubMed1998

Mechanism of brain protection by nitroxide radicals in experimental model of closed-head injury.

Reactive oxygen-derived species were previously implicated in mediation of post-traumatic brain damage; however, the efficacy of traditional antioxidants in preventing/reversing the damage is sometimes limited. The present work focused on the mechanisms underlying the neuroprotective activity of cell permeable, nontoxic, antioxidants, namely stable nitroxide radicals in an experimental model of rat closed-head injury. Brain damage was induced by the weight-drop method and the clinical status was evaluated according to a neurological severity score at 1 h and 24 h, where the difference between these scores reflects the extent of recovery. The metal chelator deferoxamine as well as three nitroxide derivatives, differing in hydrophilicity and charge, and one hydroxylamine (a reduced nitroxide) facilitated the clinical recovery and decreased the brain edema. The nitroxides, but neither the hydroxylamine nor deferoxamine, protected the integrity of the blood-brain barrier. Superoxide dismutase also improved the clinical recovery but did not affect brain edema or the blood-brain barrier. The results suggest that by switching back and forth between themselves, the nitroxide and hydroxylamine act catalytically as self-replenishing antioxidants, and protect brain tissue by terminating radical-chain reactions, oxidizing deleterious metal ions, and by removal of intracellular superoxide.

Animals↗