Biomedical subjects

Y Tang

Publications and source records attributed to Y Tang.

At least 253 records · Page 14Linked to original sources

PubMed1998

Role of endothelin in thrombolysis in rat abdominal aorta.

The endothelium of blood vessels is of great importance in maintaining blood fluidity and modulating thrombogenesis. Endothelin (ET) participates in thrombogenesis and its role in the pathogenesis of heart diseases such as acute myocardinal infarction has been proved, but little is known about the effect of ET on thrombolysis. Using a model of thrombosis in rat abdominal aorta induced by direct current-ferric trichloride, we found that the plasma ET level was 3.7 times the baseline after lysing the thrombus with urokinase (250,000 U/kg) while 5 micrograms/kg of exogenous ET prolonged the time of thrombolysis to 115% of baseline control. Plasma ET level was six times the baseline level. Incubation of a rat aortic strip in vitro with taurine (20 mmol/L) had no effect on baseline ET release, but taurine prohibited the stimulation of thrombin and A23187 of ET release in a dose-dependent way. Plasma ET decreased between 17 and 40% after injection of taurine, which also decreased by 45% the time of lysis of thrombus. From the above data it might be concluded that ET inhibits thrombolysis and that the abnormally increasing plasma ET can be attenuated by taurine, which is beneficial to thrombolysis.

Animals↗

PubMed1998

Propofol block of cardiac sodium currents in rat isolated myocardial cells is increased at depolarized resting potentials.

1. The effect of propofol on cardiac whole-cell sodium currents and single sodium channels in rat isolated ventricular myocytes was examined using patch-clamp techniques. 2. Propofol caused a block of the whole-cell sodium current, the potency of block depending on the holding potential. When cells were held at -90 mV, the EC50 was 2.8 micrograms/mL. When cells were held more hyperpolarized (at -140 mV), the EC50 increased to 44.0 micrograms/mL. 3. Although the degree of block produced by the same concentration of propofol was different at different holding potentials, the time course of onset and recovery from block was the same. 4. The current/voltage relationship for the sodium current showed a pronounced block of peak current by propofol (40-50% block of the maximum current by 30 micrograms/mL propofol), with a minimal shift in the voltage dependence of activation and no shift in reversal potential. 5. The voltage dependence of the steady state inactivation curve was shifted to more hyperpolarized potentials by propofol (shift of 18 and 8 mV by 30 and 10 micrograms/mL propofol, respectively). 6. Single channel records showed that propofol caused a shortening of the mean channel open time (from a mean of 0.59 to 0.38 ms by 10 micrograms/mL propofol), but no change in the channel amplitude. 7. It is concluded that propofol produces a block of sodium currents in cardiac myocytes at concentrations that are comparable to those that may be attained during anaesthesia.

Anesthetics, Intravenous↗

PubMed1998

Regulation of lipid synthesis in Bradyrhizobium japonicum: low oxygen concentrations trigger phosphatidylinositol biosynthesis.

Lowering oxygen tension in free-living Bradyrhizobium japonicum resulted in a dramatic switch of membrane chemistry in which phosphatidylcholine, the predominant lipid in aerated cultures, was no longer synthesized and phosphatidylethanolamine became the major lipid. Besides this change, phosphatidylinositol, a typical plant lipid rarely found in bacteria, was also synthesized.

Lipids↗

PubMed1998

Binding of murine leukemia virus Gag polyproteins to KIF4, a microtubule-based motor protein.

A cDNA clone encoding a cellular protein that interacts with murine leukemia virus (MuLV) Gag proteins was isolated from a T-cell lymphoma library. The sequence of the clone is identical to the C terminus of a cellular protein, KIF4, a microtubule-associated motor protein that belongs to the kinesin superfamily. KIF4-MuLV Gag associations have been detected in vitro and in vivo in mammalian cells. We suggest that KIF4 could be involved in Gag polyprotein translocation from the cytoplasm to the cell membrane.

Animals↗

PubMed1998

An exposed KID-like domain in human T-cell lymphotropic virus type 1 Tax is responsible for the recruitment of coactivators CBP/p300.

Human T-cell lymphotropic virus type 1 (HTLV-1) transcriptional activation is mediated by the viral transactivator, Tax, and three 21-bp repeats (Tax response element [TxRE]) located in the U3 region of the viral long terminal repeat (LTR). Each TxRE contains a core cyclic AMP response element (CRE) flanked by 5' G-rich and 3' C-rich sequences. The TxRE binds CREB (CRE-binding protein) and Tax to form a ternary complex and confers Tax-dependent transactivation. Recent data indicate that Tax functions as a specific link to connect CREB-binding protein (CBP)/p300 in a phosphorylation-independent manner to CREB/ATF-1 assembled on the viral 21-bp repeats. Glutathione S-transferase pull-down performed with Tax deletion mutants and peptide competition have localized the site in Tax critical for binding CBP/p300 to a highly protease-sensitive region around amino acid residues 81 to 95 (81QRTSKTLKVLTPPIT95) which lies between the domains previously proposed to be important for CREB binding and Tax subunit dimerization. Amino acid residues around the trypsin- and chymotrypsin-sensitive sites (88KVL90) of Tax bear resemblance to those in the kinase-inducible domain of CREB (129SRRPSYRKILNE140) surrounding Ser-133, which undergoes signal-induced phosphorylation to recruit CBP/p300. Site-directed mutagenesis of residues in this domain (R82A, K85A, K88A, and V89A) resulted in proteins which failed to transactivate from the HTLV-1 LTR in vivo. These mutants (K85A, K88A, and V89A) bind CREB with similar affinities as wild-type Tax, yet interaction with CBP/p300 is abrogated in various biochemical assays, indicating that the recruitment of CBP/p300 is crucial for Tax transactivation. A Tax mutant, M47, defective in the COOH-terminal transactivation domain, continued to interact with CBP/p300, suggesting that interactions with additional cellular factors are required for proper Tax function.

Amino Acid Sequence↗

PubMed1998

MR imaging of the liver: comparison between single-shot echo-planar and half-Fourier rapid acquisition with relaxation enhancement sequences.

PURPOSE: To evaluate single-shot T2-weighted magnetic resonance sequences and their role in clinical practice in patients with hepatic lesions. MATERIALS AND METHODS: Prospective comparison of echo-planar and half-Fourier rapid acquisition with relaxation enhancement (RARE) imaging was performed in 80 patients with focal hepatic lesions. Spin-echo (SE) single-shot echo-planar (echo times, 47 and 80 msec) and half-Fourier RARE (echo time, 59 msec) images were compared with turbo SE (repetition time msec/echo time msec = 3,200-7,600/90) images. Quantitative, qualitative, and receiver operating characteristic (ROC) analyses were performed. RESULTS: For liver, signal-to-noise ratios on half-Fourier RARE images were significantly higher than those on echo-planar images (P < .01). For cystic lesions, contrast on half-Fourier RARE and echo-planar images was slightly higher than that on turbo SE images. For solid lesions, contrast on echo-planar images was better than that on half-Fourier RARE or turbo SE images. Artifacts including ghosting, bowel motion, susceptibility difference, and chemical shift were negligible on half-Fourier RARE images in all patients, whereas susceptibility difference and chemical shift of various degrees were seen on all echo-planar images. On the basis of ROC analyses, tumor detection rates were significantly higher with half-Fourier RARE and turbo SE images than with echo-planar images (P < .01). CONCLUSION: Echo-planar images provide sufficient contrast to allow detection of both solid and cystic masses, but severe artifacts preclude routine use. Half-Fourier RARE images are free from artifacts (chemical shift and susceptibility) and diagnostic performance with them is similar to that with turbo SE images.

Adult↗

PubMed1998

Determination of concentration of cytosolic NADH-cytochrome b5 reductase in erythrocytes from normal Chinese adults, neonates and patients with hereditary methemoglobinemia by double-antibody sandwich ELISA.

NADH-cytochrome b5 reductase (b5R), present in various tissues of the body, is a redox enzyme of multiple functions. The deficiency of the enzyme leads to hereditary methemoglobinemia. With rabbit anti-b5R antibody for plate coating and enzyme-labeled anti-b5R monoclonal antibody as reporter, we have developed a sandwich ELISA procedure for the determination of b5R concentration. This procedure is sensitive to a wide range of linearity, and convenient in coping with large numbers of samples. Using this novel method, cytosolic b5R concentration in the erythrocytes of 30 normal Chinese adults was estimated to be 25.63+/-8.54 ng/mg Hb. It was found that the concentration of red cell soluble b5R of five newborns was significantly lower than that of normal adults and soluble b5R was undetectable in the erythrocytes of 4 patients with type I hereditary methemoglobinemia. Our results demonstrated that the reduced b5R activity in red cell cytosol of both neonates and type I hereditary methemoglobinemic patients results largely or mainly from the lowered b5R concentration. Our novel method might be further exploited for in-depth investigation of the relationship between the qualitative and quantitative changes of b5R with regard to physiological and pathological conditions.

Adult↗

PubMed1998

The DNA-binding and tau2 transactivation domains of the rat glucocorticoid receptor constitute a nuclear matrix-targeting signal.

Using an ATP-depletion paradigm to augment glucocorticoid receptor (GR) binding to the nuclear matrix, we have identified a minimal segment of the receptor that constitutes a nuclear matrix targeting signal (NMTS). While previous studies implicated a role for the receptor's DNA-binding domain in nuclear matrix targeting, we show here that this domain of rat GR is necessary, but not sufficient, for matrix targeting. A minimal NMTS can be generated by linking the rat GR DNA-binding domain to either its tau2 transactivation domain in its natural context, or a heterologous transactivation domain derived from the Herpes simplex virus VP16 protein. The transactivation and nuclear matrix-targeting activities of tau2 are separable, as transactivation mutants were identified that either inhibited or had no apparent effect on matrix targeting of tau2. A functional interaction between the NMTS of rat GR and the RNA-binding nuclear matrix protein hnRNP U was revealed in cotransfection experiments in which hnRNP U overexpression was found to interfere with the transactivation activity of GR derivatives that possess nuclear matrix-binding capacity. We have therefore ascribed a novel function to a steroid hormone transactivation domain that could be an important component of the mechanism used by steroid hormone receptors to regulate genes in their native configuration within the nucleus.

Adenosine Triphosphate↗

PubMed1998

Galactosyltransferase, pyrophosphatase and phosphatase activities in luminal plasma of the cauda epididymidis and in the rete testis fluid of some mammals.

Galactosyltransferase activity was measured in the luminal plasma of the cauda epididymidis of mice, rats, rabbits, rams and boars, and in the rete testis fluid of rams and boars. The activities of nucleotide pyrophosphatase and alkaline phosphatase, which compete with galactosyltransferase for substrate, were also determined. In these species, galactosyltransferase activity in the luminal plasma of the cauda epididymidis was similar when the inhibitory effect of pyrophosphatase and phosphatase was minimized by assay conditions. However, under assay conditions that did not minimize the effect of these enzymes, the galactosyltransferase activities of these species were very different and were inversely correlated with the activities of pyrophosphatase and phosphatase. The ratio of galactosyltransferase activity to pyrophosphatase and phosphatase activity was much higher in the rete testis fluid than in the luminal plasma of the cauda epididymidis in both rams and boars. In rams, galactosyltransferase in the luminal plasma of the cauda epididymidis was more heat resistant than that in serum. These results suggest that there is a species difference in the availability of galactosyltransferase activity in the luminal plasma of the cauda epididymidis and that in some species, galactosyltransferase in the luminal fluid is unlikely to have any function. The results are also discussed with respect to the possible function of galactosyltransferase, pyrophosphatase and phosphatase in epididymal luminal plasma and rete testis fluid.

Alkaline Phosphatase↗

PubMed1998

Single-shot MR cholangiopancreatography of neonates, infants, and young children.

OBJECTIVE: This study was undertaken to assess the usefulness of MR cholangiopancreatography (MRCP) with a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence as a noninvasive imaging technique to evaluate biliary or pancreatic disease in young children. SUBJECTS AND METHODS: We prospectively examined 45 children (mean age, 3 years) with MRCP using HASTE on a 1.5-T MR imaging unit. MRCP images were obtained in 1.4 sec without breath-hold. A body phased array coil and fat saturation technique were used for data collection. On the basis of the surgical (n = 19) and ERCP (n = 7) findings, clinical data, and follow-up observation, 21 children were deemed to have no significant abnormality. The other 24 children were found to have pancreaticobiliary disease, including congenital biliary atresia in five neonates, choledochal cyst in six infants, and anomalous connections between the bile and pancreatic ducts in four infants and nine young children. In children without abnormality, the MRCP images were graded for the depiction of normal structures. The findings obtained by MRCP were correlated with the surgical or ERCP results. RESULTS: HASTE MRCP showed the first branch of the intrahepatic duct, the common hepatic duct, the gallbladder, and the common bile duct in most children. In the 21 children with no abnormalities, the main pancreatic duct was visible in two of six neonates, in four of five infants, and in all 10 young children. The diagnostic accuracy of MRCP was 100% in patients with choledochal cysts, 100% in those with congenital biliary atresia, and 69% in those with anomalous connections between the bile and pancreatic ducts. CONCLUSION: MRCP using HASTE with a phased array coil is a noninvasive technique for revealing the pancreaticobiliary tract in young children.

Biliary Atresia↗

PubMed1998

Statistical evaluation of in vitro dissolution of different brands of ciprofloxacin hydrochloride tablets and capsules.

The in vitro dissolution of ciprofloxacin from commercially available tablets and capsules in China was studied using the USP apparatus I to compare the product performance from nine different manufacturers. Cumulative release greater than 75% was obtained from all of the products tested within 45 min. However, statistically significant differences were found between some of the products when in vitro data were analyzed using the Weibull function, similarity factor (f2), and multivariate analysis of variances.

Anti-Infective Agents↗

PubMed1998

[Glutathione S-transferase M1, T1 genotypes and the risk of esophageal cancer: a case-control study].

To examine the association between genetic polymorphisms of glutathione S-transferase (GST) M1 and T1 and susceptibility to esophageal cancer, a multiplex polymerase chain reaction method was used to detect the presence or absence of the GSTM1 and GSTT1 genes in genomic DNA isolated from surgically removed esophageal tissues or scraped esophageal cells from cases with cancer (n = 45), cases with severe hyperplasia (n = 45), and sex/age matched normal controls (n = 45) from a high risk area, Linxian, China. Results showed that the frequency of the GSTM1-null genotype in cancer cases (44.4%) or hyperplasia cases (44.4%) was not significantly different from that in controls (46.7%). Similarly, no statistically significant differences were observed in the frequency of GSTT1-null genotype in cancer cases (40.0%) or hyperplasia cases (37.8%) when compared with the controlled population (51.1%). However, the frequency of combined GSTM1-nonnull and GSTT1-nonnull genotypes in cases with cancer (40.0%) and cases with hyperplasia (37.8%) showed a significant increase compared to that in controls (22.2%). Persons with both GSTM1 and GSTT1 positive genotypes had 4-fold risk in developing esophageal cancer (odds ratio, OR = 4.20; 95% confidence interval, CI = 1.23-14.36) and 2.6-fold risk for hyperplasia (OR = 2.64; 95% CI = 0.84-8.30), respectively. These results suggest that combined GSTM1-nonnull and GSTT1-nonnull genotypes may act as risk factor in the development of esophageal cancer in Linxian population.

Adult↗

PubMed1998

[Monitoring and management on the mandatory reporting system of infectious diseases in Jiangxi provincial].

From 1994 to 1997, we had continuously and actively conducted surveillance on reports of legal infectious diseases and administrative performance of hospitals in this aspect. The proportion from outpatient clinic in the whole province under supervision had sucessively increased yearly. It suggested that the implementation of "report on the first visit" regulation had been improved; the number of hospitals with "no information on epidemic desease" had decreased, and the number of months with no information on epidemic disease had also decreased. All the results showed that the surveillance and monitoring on the infectious desease reporting system and administrative performance of hospitals was an effective practice.

China↗

PubMed1998

Establishment of kappa opioid receptor agonists pharmacophore with molecular modeling method.

AIM: To build up nonpeptide kappa-opioid receptor agonists pharmacophore. METHODS: Five structurally diverse, highly active nonpeptide kappa-opioid agonists were retrieved from MDL MDDR database. Molecular mechanics method were used to seek out 50 lower energy conformations for each compound. Taking nitrogen atom of pyrrolidine and acyl acetamide as overlay points, 5 agonists were superimposed to each other with their most favorite conformation. From the overlay map, the structure specificity of nonpeptide kappa-opioid receptor agonists were elucidated. RESULTS: According to this pharmacophore, the pyrrolidine ring, the carbonyl group of acyl acetamide, and the hydrophobic group attached to acyl acetamide were suggested to be the structure-specific moieties of kappa-opioid agonists. Moreover, by comparing kappa 1-opioid receptor sequence of mouse with other G-protein-coupled receptors, we determined those conserve residues existing on transmembrane regions which might interact with the suggested groups. The carboxyl of Asp138 might interact with N atom of pyrrolidine by forming a hydrogen bond. The hydroxyl of Ser187 and the carbonyl group of kappa-opioid agonists might form another hydrogen bond, which was critical for its kappa selective affinity. The hydrophobic group attached to acyl acetamide might have hydrophobic interaction with aromatic residues of kappa-opioid receptors. CONCLUSION: These kappa agonists pharmacophore were helpful to select specific positions in the lead compounds to be occupied by hydrophobic moieties to limit their ability to across the blood-brain barrier.

Amino Acid Sequence↗

PubMed1998

[Genetic polymorphisms of cytochrome P450 2E1 and glutathione S-transferase P1 and susceptibility to esophageal cancer].

OBJECTIVES: To study the association between genetic polymorphisms of cytochrome P4502E1 (CYP2E1) and/or glutathione S-transferase P1 (GSTP1) and susceptibility to esophageal cancer. METHODS: Genotyping of CYP2E1 and GSTP1 was performed using PCR-based RFLP analysis on DNA isolated from surgically removed esophageal tissues or scraped esophageal epithelium from cancer cases (n = 45), severe epithelial hyperplasia cases (n = 45), and normal controls (n = 45). RESULTS: The variant genotypes (c1/c2 and c2/c2) detected by RsaI digestion was found in 17% of epithelial hyperplasia cases, 20.0% of esophageal cancer cases and 55.6% of controls, with the differences being statistically significant (P < 0.001). Subjects carrying wild-type genotype of CYP2E1 had more than 5-fold risk for developing severe epithelial hyperplasia (odds ratio, OR = 5.78; 95% confidence interval, CI = 2.2-15.2) and esophageal cancer (OR = 5.00; 95% CI = 2.0-12.8). No association with the risk of severe epithelial hyperplasia and esophageal cancer was observed for the DraI polymorphism of CYP2E1 or for the Awl26I polymorphism of GSTP1. CONCLUSION: CYP2E1 is a genetic susceptibility factor involved in the early events for esophageal carcinogenesis.

Adult↗

PubMed1998

[Brain cell apoptosis after cerebral hypoxia-ischemia in neonatal rat].

OBJECTIVE: To investigate action of apoptosis in mechanisms of neonatal hypoxia-ischemia (HIE). METHODS: Using HE staining, electronmicroscope, and terminal deoxynuleotidyl transferase-mediated dUTP nick end labeling (TUNEL) technique, we observed the histological features, time course and density of apoptotic cells and compared the ipsilateral hemisphere after permanent ischemia 1, 4, 18, 24, 40, 72 h, 7 days after 3 h hypoxia with that of sham-group. RESULTS: Neurons in the cortex, hippocampus, thalamus exhibited cells shrink, chromatin condensation, apoptosis bodys under microscope, as demonstrated by in situ labeling of DNA breaks. The peak for apoptosis was shown at 18 h in the cortex. CONCLUSION: In the HIE, apoptosis appears earlier than necrosis, and both of the different cell death forms may exist induced dose relativity.

Animals↗

PubMed1998

[Effect of kidney yin-yang replenishing Chinese herbs on the binding character of insulin receptor on hepatocyte membrane in androgen-induced sterility rats].

OBJECTIVE: To observe the effect of Kidney Yin-Yang replenishing Chinese herbs on the binding character of insulin receptor (IR) on hepatocyte membrane from androgen-induced sterility rats (ASR). METHODS: The number and affinity of IR on hepatocyte membrane of ASR were determined with radioligand binding assay. RESULTS: There was no significant difference of the number or affinity for both high and low affinity sites of IR between normal and ASR. CONCLUSION: The treatment with Kidney Yin-Yang replenishing Chinese herbs had no effect on insulin binding although a relatively high rate of ovulation induction on ASR was observed.

Animals↗

PubMed1998

[Synthesis and bioaction of 2-alkyl-4(1H)-quinolone].

Five quinolone alkaloids (IVa, Va, c, d, g) including two new compounds (IVa, Vc) from Evodia rutaecarpa and nine analogs are synthesized in good yield by using acid-catalyzed condensation of a series of 3-oxoalkkanoic acid esters with aniline and further methylized with methyl iodide. The other analogue Vh is prepared through the reaction of lithium enolate methyl ketone with N-methylisatoic anhydride. Eight compounds (IVa, d, f; Vb, c, d, f, h) were synthesized for the first time. Pharmacological studies showed that these compounds have vasoconstriction inhibiting and antiulcer effects. Compound IVb also has cytotoxic effect.

Alkaloids↗