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Biomedical subjects

Y L Zhu

Publications and source records attributed to Y L Zhu.

At least 19 recordsLinked to original sources
PubMed2003

Electrochemical behavior and detection of hepatitis B virus DNA PCR production at gold electrode.

Sequence-known short-stranded hepatitis B virus (HBV) DNA fragment (181 bps) was obtained by PCR method. The strategy for its electrochemical detection was designed by covalently immobilizing single-stranded HBV DNA on gold electrode surface via carboxylate ester as a linkage between 3'-hydroxy end of DNA and carboxyl group of thioglycolic acid (TGA) self-assembled monolayer. The hybridization reaction on surface was evidenced by electrochemical methods using ferrocenium hexafluorophosphate (FcPF6) as an electroactive indicator. The interactions of Fc+ with single-stranded (ss) and double-stranded (ds) HBV DNA immobilized on TGA monolayer were studied. The difference between the responses of Fc+ at ss- and ds-DNA/Au electrodes suggested that this hybridization biosensor could be conveniently used to monitor DNA hybridization with a high sensitivity. AC impedance and XPS techniques have been employed to characterize the immobilization of ss-DNA on the gold surface.

Adsorption↗
PubMed2003

Single-nucleotide polymorphisms in soybean.

Single-nucleotide polymorphisms (SNPs) provide an abundant source of DNA polymorphisms in a number of eukaryotic species. Information on the frequency, nature, and distribution of SNPs in plant genomes is limited. Thus, our objectives were (1) to determine SNP frequency in coding and noncoding soybean (Glycine max L. Merr.) DNA sequence amplified from genomic DNA using PCR primers designed to complete genes, cDNAs, and random genomic sequence; (2) to characterize haplotype variation in these sequences; and (3) to provide initial estimates of linkage disequilibrium (LD) in soybean. Approximately 28.7 kbp of coding sequence, 37.9 kbp of noncoding perigenic DNA, and 9.7 kbp of random noncoding genomic DNA were sequenced in each of 25 diverse soybean genotypes. Over the >76 kbp, mean nucleotide diversity expressed as Watterson's theta was 0.00097. Nucleotide diversity was 0.00053 and 0.00111 in coding and in noncoding perigenic DNA, respectively, lower than estimates in the autogamous model species Arabidopsis thaliana. Haplotype analysis of SNP-containing fragments revealed a deficiency of haplotypes vs. the number that would be anticipated at linkage equilibrium. In 49 fragments with three or more SNPs, five haplotypes were present in one fragment while four or less were present in the remaining 48, thereby supporting the suggestion of relatively limited genetic variation in cultivated soybean. Squared allele-frequency correlations (r(2)) among haplotypes at 54 loci with two or more SNPs indicated low genome-wide LD. The low level of LD and the limited haplotype diversity suggested that the genome of any given soybean accession is a mosaic of three or four haplotypes. To facilitate SNP discovery and the development of a transcript map, subsets of four to six diverse genotypes, whose sequence analysis would permit the discovery of at least 75% of all SNPs present in the 25 genotypes as well as 90% of the common (frequency >0.10) SNPs, were identified.

DNA Primers↗
PubMed2001

Acquisition of Lubrol insolubility, a common step for growth hormone and prolactin in the secretory pathway of neuroendocrine cells.

Rat prolactin in the dense cores of secretory granules of the pituitary gland is a Lubrol-insoluble aggregate. In GH(4)C(1) cells, newly synthesized rat prolactin and growth hormone were soluble, but after 30 min about 40% converted to a Lubrol-insoluble form. Transport from the endoplasmic reticulum is necessary for conversion to Lubrol insolubility, since incubating cells with brefeldin A or at 15 degrees C reduced formation of insoluble rat (35)S-prolactin. Formation of Lubrol-insoluble aggregates has protein and cell specificity; newly synthesized human growth hormone expressed in AtT20 cells underwent a 40% conversion to Lubrol insolubility with time, but albumin did not, and human growth hormone expressed in COS cells underwent less than 10% conversion to Lubrol insolubility. del32-46 growth hormone, a naturally occurring form of growth hormone, and P89L growth hormone underwent conversion, although they were secreted more slowly, indicating that there is some tolerance in structural requirements for aggregation. An intracellular compartment with an acidic pH is not necessary for conversion to Lubrol insolubility, because incubation with chloroquine or bafilomycin slowed, but did not prevent, the conversion. GH(4)C(1) cells treated with estradiol, insulin, and epidermal growth factor accumulate more secretory granules and store more prolactin, but not more growth hormone, than untreated cells; Lubrol-insoluble aggregates of prolactin and growth hormone formed to the same extent in hormone-treated or untreated GH(4)C(1) cells, but prolactin was retained longer in hormone-treated cells. These findings indicate that aggregation alone is not sufficient to cause retention of secretory granule proteins, and there is an additional selective process.

Animals↗
PubMed2001

Signaling pathway mediated by kappa-opioid receptor is impaired in cardiac hypertrophy.

AIM: The responses of the intracellular calcium ([Ca2+]i) and the intracellular pH (pHi) to kappa-opioid receptor stimulation were determined in the single right ventricular myocytes isolated from the hearts of chronically hypoxic rats which exhibited right ventricular hypertrophy (RVH). METHODS: With the spectrofluorometric method, the electrically-induced [Ca2+]i transient and pHi were measured in myocytes loaded with fura-2 and BCECF [2',7'-bis-(2-carboxyethyl)-5-(and 6)-carboxyfluorscein], respectively. RESULTS: U50,488H, a selective kappa-opioid agonist decreased the electrically-induced [Ca2+]i transient and increased the pHi. The effect of U50,488H was mediated by protein kinase C (PKC). In the RVH, the effect of U50,488H on the [Ca2+]i transient and the pHi were significantly attenuated. In parallel, 4-phorbol 12-myristate 13-acetate (PMA), an activator of PKC, also decreased the [Ca2+]i transient and increased the pHi. In the RVH, the effects of PMA were blunted. The recovery of pHi, which was blocked by ethylisopropyl-amiloride (EIPA), following an acid loading induced by washout of 10 mmol/L NH4)Cl exposing to the cells for 10 min was the same in the RVH and control myocytes. CONCLUSION: kappa-Opioid receptor signaling was impaired in the cardiac hypertrophy due to a defect in the coupling of PKC signaling with its effector.

Animals↗
PubMed2000

Accumulation of synaptosomal-associated protein of 25 kDa (SNAP-25) and other proteins associated with the secretory pathway in GH4C1 cells upon treatment with estradiol, insulin, and epidermal growth factor.

Treatment of rat pituitary GH4C1 cells with estradiol, insulin, and epidermal growth factor induces secretory granule accumulation, PRL storage, and stabilization of ICA512, a membrane protein associated with secretory granules. In these investigations we found that the same treatment induced accumulation over 2-fold of other proteins in the secretory pathway, including synaptosomal-associated protein of 25 kDa (SNAP-25), synaptotagmin III, synaptobrevin, synaptophysin, and cyclophilin B, and did not affect accumulation of others, including synaptotagmin I, calnexin, and glucose-regulated protein 94. The induction of proteins was not a coordinate event, because epidermal growth factor alone maximally stimulated SNAP-25 accumulation, but not that of synaptotagmin III. Induction of SNAP-25 accumulation occurred without an increase in its synthesis, and induction of cyclophilin B occurred without an increase in its messenger RNA accumulation, suggesting that accumulation may be caused by stabilization of the proteins. SNAP-25 immunofluorescence was located in the cytoplasm and on the plasma membrane and sometimes was heavily concentrated in protrusions from the cell surface, especially in hormone-treated cells. Frequenin immunofluorescence was also sometimes concentrated in intense patches, but did not colocalize with SNAP-25. Growth hormone and prolactin immunofluorescence was not found in the protrusions and sometimes did not colocalize with each other when they were present in the same cell. Hormone treatment of GH4C1 cells therefore induces accumulation of specific proteins in all parts of the secretory pathway and causes morphological changes in addition to accumulating secretory granules.

Animals↗
PubMed2000

[Effect of interleukin 2 on the expression of estrogen receptors in the anterior pituitary of rats].

Using primary serum-free cell culture combined with immunocytochemistry and semi-quantified RT-PCR methods, we observe the modulation of estrogen receptor alpha (ERalpha) and beta (ERbeta) by interleukin-2 (IL-2) in rat anterior pituitary. The results show that IL-2 up-regulates the level of ERalpha protein and the expression of ERalpha mRNA, but down-regulates those of ERbeta. The density per cell of ERalpha-immunoreactive (ir) cells increases from 48.740 4.567 to 81.188+/-6.619, whereas that of ERbeta -ir cells decreases from 102.560+/-6.250 to 72.718+/-7.623 after rhIL-2 (10 microgram/L) incubation for 48 h. In parallel with these changes, the ratio of ERalpha/ beta -actin mRNA increases from 0.1511 to 0.4334, and ERbeta /beta -actin mRNA declines from 0.3822 to 0.1528. It is likely that IL-2 has direct regulatory effect on ER in anterior pituitary.

Animals↗
PubMed2000

[Interleukin-2 stimulates the proliferation of cultured RC-4B/C pituitary adenoma cell line].

The aim of the present study was to investigate whether interleukin-2 (IL-2) is involved in the proliferation control of the cultured RC-4B/C cell, which is a derived pituitary adenoma cell line of the rat. The level of cell proliferation was estimated by assessing (3)H-thymidine ((3)H-TdR) incorporation rate. IL-2 (10 1000 U/ml) significantly stimulated (3)H-TdR incorporation into the cell line in a dose-dependent manner. Specific PTK inhibitor tyrphostin (1 micromol/L) suppressed RC-4B/C cell proliferation and blocked the effect of IL-2 on RC-4B/C cells. After the PKA signaling pathway was inhibited by specific PKA inhibitor H-9 (1 micromol/L), the proliferation rate of RC-4B/C cells increased significantly. H-9 also enhanced the stimulation of IL-2 on RC-4B/C cell growth. Anti-estrogen tamoxifen (1 micromol/L) had no significant effect on the action of IL-2 on the proliferation of RC-4B/C cells. In conclusion, it is suggested that IL-2 modulates the proliferation of the cultured RC-4B/C pituitary adenoma cell line, and the action is closely related with the PTK and PKA signaling pathway.

Adenoma↗
PubMed1999

Cadmium tolerance and accumulation in Indian mustard is enhanced by overexpressing gamma-glutamylcysteine synthetase.

To investigate rate-limiting factors for glutathione and phytochelatin (PC) production and the importance of these compounds for heavy metal tolerance, Indian mustard (Brassica juncea) was genetically engineered to overexpress the Escherichia coli gshI gene encoding gamma-glutamylcysteine synthetase (gamma-ECS), targeted to the plastids. The gamma-ECS transgenic seedlings showed increased tolerance to Cd and had higher concentrations of PCs, gamma-GluCys, glutathione, and total non-protein thiols compared with wild-type (WT) seedlings. When tested in a hydroponic system, gamma-ECS mature plants accumulated more Cd than WT plants: shoot Cd concentrations were 40% to 90% higher. In spite of their higher tissue Cd concentration, the gamma-ECS plants grew better in the presence of Cd than WT. We conclude that overexpression of gamma-ECS increases biosynthesis of glutathione and PCs, which in turn enhances Cd tolerance and accumulation. Thus, overexpression of gamma-ECS appears to be a promising strategy for the production of plants with superior heavy metal phytoremediation capacity.

Cadmium↗
PubMed1998

Anti-hepatitis B virus activity and metabolism of 2',3'-dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine.

2',3'-Dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine [L(-)Fd4C] was found to be at least 10 times more potent than beta-L-2',3'-dideoxy-3'-thiacytidine [L(-)SddC; also called 3TC, or lamivudine]against hepatitis B virus (HBV) in culture. Its cytotoxicity against HepG2 growth in culture was also greater than that of L(-)SddC (3TC). There was no activity of this compound against mitochondrial DNA synthesis in cells at concentrations upto 10 microM. The dynamics of recovery of virus from the medium of cells pretreated with equal drug concentrations were slower with L(-)Fd4C than with L(-)SddC (3TC). L(-)Fd4C could be metabolized to mono-, di-, and triphosphate forms. The degree of L(-)Fd4C phosphorylation to the 5'-triphosphate metabolite was higher than the degree of L(-)SddC (3TC) phosphorylation when equal extracellular concentrations of the two drugs were used. The apparent K(m) of L(-)Fd4C phosphorylated metabolites formed intracellularly was higher than that for L(-)SddC (3TC). This may be due in part to a difference in the behavior of L(-)Fd4C and L(-)SddC (3TC) towards cytosolic deoxycytidine kinase. Furthermore, L(-)Fd4C 5'-triphosphate was retained longer within cells than L(-)SddC (3TC) 5-triphosphate. L(-)Fd4C 5'-triphosphate inhibited HBV DNA polymerase in competition with dCTP with a Ki of 0.069 +/- 0.015 microM. Given the antiviral potency and unique pharmacodynamic properties of L(-)Fd4C, this compound should be considered for development as an expanded-spectrum anti-HBV drug.

Antiviral Agents↗
PubMed1997

Inhibition of replication of hepatitis B virus by cytallene in vitro.

The acyclic cytosine nucleoside analog cytallene [1-(4'-hydroxy-1',2'-butadienyl)cytosine], which has both (+)- and (-)-enantiomers, was evaluated for its anti-hepatitis B virus (HBV) activity in 2.2.15 cells and was found to have potent activity against HBV DNA synthesis. The R-(-)-enantiomer was found to be the more active of the cytallene enantiomers, with a 50% inhibition concentration against HBV synthesis (HBIC50) of 0.08 microM. Its antiviral activity could be reversed by deoxycytidine (dC) and less efficiently by cytidine. Upon removal of the R-(-)-enantiomer from culture medium, the synthesis of HBV DNA could reinitiate, which suggested that the antiviral action is reversible. The R-(-)-enantiomer was also found to be more cytotoxic than the S-(+)-enantiomer. The degree of cytotoxicity varied among the cell lines, with a 50% inhibition of cell growth at greater than 10 microM. The R-(-)-enantiomer had no effect on HBV RNA synthesis and mitochondrial DNA synthesis at a concentration of 10 times or more than the HBIC50. The two enantiomers cannot be deaminated by dC deaminase, and they can be phosphorylated by cytoplasmic dC kinase. The R-(-)-enantiomer of cytallene is the first acyclic cytosine analog with potent inhibitory activity against HBV similar to those of other L-(-)-ddC analogs.

Antiviral Agents↗
PubMed1997

[An investigation on anxiety and coping patterns of patients under cancer chemotherapy and the strategies].

100 cases of patients under cancer chemotherapy were investigated by using Self-Rating Anxiety Scale (SAS) and questionnaire on coping patterns. The results showed that scores of SAS were significantly higher than that of the normal population. The state of the anxiety reached 45% among the patients. The patients' coping patterns tended to be passive. Linear analysis revealed a negative correlation between the coping patterns and the scores of SAS. It is recommended that cognitive behavioral therapy can be used to relieve the anxiety of patients under cancer chemotherapy.

Adaptation, Psychological↗
PubMed1997

[Effect of interleukin-2 on the proliferation of cultured rat anterior pituitary cells].

The present study was to investigate whether IL-2 is involved in the proliferation control of anterior pituitary (AP) cells. Primary culture of AP cells was obtained from either male or female Sprague-Dawley rats. The effects of IL-2 were assessed by 3H-thymidine incorporation rate. It was found that: (1) IL-2 (10-500 U/ml) significantly stimulated 3H-TdR incorporation into AP cells of female pregnant as well as none-pregnant rats, but inhibited 3H-TdR incorporation in the male rats. (2) The stimulatory effect of IL-2 was reversed in overiectomized rats, but could be restored when the overiectomized rats were treated with estradiol benzoate (5 micrograms/d per rat). (3) When the male rats were orchiectomized for 2 weeks, the inhibitory effects of IL-2 did not occur. The above data indicated that the proliferative effect of IL-2 on AP is a joint action of sex steroids hormones.

Animals↗
PubMed1996

Structure--activity relationships of 1-(2-Deoxy-2-fluoro-beta-L-arabinofuranosyl)pyrimidine nucleosides as anti-hepatitis B virus agents.

Since 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU) has been shown to be a potent anti-HBV agent in vitro, it was of interest to study the structure-activity relationships of related nucleosides. Thus, a series of 1-(2-deoxy-2-fluoro-beta-L-arabinofuranosyl)pyrimidine nucleosides have been synthesized and evaluated for antiviral activity against HBV in 2.2.15 cells. For this study, L-ribose was initially used as the starting material. Due to the commercial cost of L-ribose, we have developed an efficient procedure for the preparation of L-ribose derivative 6. Starting from L-xylose, 6 was obtained in an excellent total yield (70%) through the pyridinium dichromate oxidation of the 3-OH group followed by stereoselective reduction with NaBH4. It was further converted to the 1,3,5-tri-O-benzoyl-2-deoxy-2-fluoro-alpha-L-arabinofuranose (10), which was then condensed with various 5-substituted pyrimidine bases to give the nucleosides. Among the compounds synthesized, the lead compound, L-FMAU (13), exhibited the most potent anti-HBV activity (EC50 0.1 microM). None of the other uracil derivatives showed significant anti-HBV activity up to 10 microM. Among the cytosine analogues, the cytosine (27) and 5-iodocytosine (35) derivatives showed moderately potent anti-HBV activity (EC50 1.4 and 5 microM, respectively). The cytotoxicity of these nucleoside analogues has also been assessed in 2.2.15 cells as well as CEM cells. None of these compounds displayed any toxicity up to 200 microM in 2.2.15 cells. Thus, compound 13 (L-FMAU), 27, and 35 showed a selectivity of over 2000, 140, and 40, respectively.

Antiviral Agents↗
PubMed1996

Inhibition of hepatitis B virus by a novel L-nucleoside, 2'-fluoro-5-methyl-beta-L-arabinofuranosyl uracil.

2'-Fluoro-5-methyl-beta-L-arabinofuranosyl uracil (L-FMAU) was discovered to have potent antiviral activity against hepatitis B virus (HBV). L-FMAU was more potent than its D-enantiomer and produced dose-dependent inhibition of the viral DNA replication in 2.2.15 cells (human HepG2 cells with the HBV genome), with a 50% inhibitory concentration of 0.1 microM. There was no inhibitory effect on HBV transcription or protein synthesis. In the 2.2.15 cell system, L-FMAU did not show any toxicity up to 200 microM, whereas the D-enantiomer was toxic, with a 50% inhibitory concentration of 50 microM. Repeated treatments of HepG2 cells with L-FMAU at a 1 microM concentration for 9 days did not result in any decrease in the total mitochondrial DNA content, suggesting that a mode of toxicity similar to that produced by 2',3'-dideoxycytidine is unlikely. Also at concentrations as high as 200 microM, L-FMAU did not adversely affect mitochondrial function as determined by lactic acid production by L-FMAU-treated hepatoma cells. L-FMAU was metabolized in the cells to its mono-, di-, and triphosphates, A dose-dependent inhibition of HBV DNA synthesis by L-FMAU triphosphate was observed in the DNA polymerase assays with isolated HBV particles, suggesting that the mode of action of this compound could involve viral polymerase. However, L-FMAU was not incorporated into the cellular DNA. Considering the potent inhibition of the viral DNA synthesis and the nontoxicity of L-FMAU towards the host DNA synthetic machinery, this compound should be further explored for development as asn anti-HBV drug.

Antiviral Agents↗
PubMed1996

[Involvement of the nerve fiber elements in the anterior pituitary in the regulation of ACTH secretion].

While peptidergic nerve fibers have been immunoreactively identified in the adenohypophysis of mammals, the function of these fibers in the regulation of hormone secretion remain unknown. The present work was undertaken to investigate possible modulating effects of these fibers on the secretion of ACTH in the anterior pituitary. Electrical field stimulation (EFS) was applied to excite the nerve terminals in anterior pituitary quarters of male rats under static incubation, and the ACTH level was determined by radioimmunoassay. It was found that the ACTH release from the anterior pituitary was significantly enhanced by EFS (30 mA, 0.5 ms and 10 Hz), which could be significantly decreased by adding TTX or veratridine into the incubation medium. However, TTX failed to inhibit AVP-induced ACTH secretion. Since the dispersed cultured anterior pituitary cells did not respond to the same EFS, it was suggested that there might exist dual modulatory mechanisms on the anterior pituitary hormone secretion.

Adrenocorticotropic Hormone↗
PubMed1996

Effects of beta-carotene on doxorubicin-induced cardiotoxicity in rats.

AIM: To study the effects of beta-carotene (Car) reducing the cardiotoxicity induced by doxorubicin (Dox). METHODS: The pathological changes of rat myocardium were observed with photomicroscopy. The malondialdehyde (MDA) value of rat heart was measured with thiobarbituric acid method. The pyrogallol autoxidation method was used for determination of superoxide dismutase (SOD) activity. The activities of glutathione peroxidase (GSH-Px) were quantitatived with DTNB method. Electron spin resonance (ESR) technique was used to measure the level of the semiquinone free radicals. RESULTS: Car 10 or 30 mg.kg-1.d-1 i.g. reduced the cardiotoxicity induced by Dox, diminished the myocardial MDA production (P < 0.01), and protected the activities of SOD and GSH-Px. ESR revealed that Car scavenged semiquinone free radicals induced by Dox in vitro. The inhibitory rates of semiquinone free radicals formation by Car 0.02, 0.1, and 1.0 mmol.L-1 were 47.7%, 76.6%, and 82.5%, respectively. CONCLUSIONS: Car, with abilities of anti-lipid peroxidation and scavenging semiquinone free radicals, possessed effects of reducing Dox-induced cardiotoxicity.

Animals↗
PubMed1994

Effects of calcium and calmodulin inhibitors on the abnormal proliferation of lung fibroblast.

The effects of alveolar macrophage (Am phi) conditioned media from interstitial lung disease (ILD) patients on fibroblast (FB), and the role of calcium (Ca2+) blockers and calmodulin (CaM) inhibitors on the proliferation of lung FB were studied. We found that the AM phi conditioned media could stimulate FB cell proliferation and this effect could be abolished by Ca2+ blockers and CaM inhibitors. The results indicated that AM phi was in activated state in ILD and released some kinds of cytokines to stimulate the proliferation of FB, and Ca,2+ CaM were partially responsible for these actions.

Bronchoalveolar Lavage Fluid↗