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Biomedical subjects

R Wang

Publications and source records attributed to R Wang.

At least 667 records · Page 37Linked to original sources
PubMed1991

[Studies on chemical constituents of Fritillaria in Hubei. XIII. Isolation and structure elucidation of hupehemonoside].

A new D/E cis-5-cevanine alkaloidal glucoside, C33H53NO8, mp 206-208 degrees C, named hupehemonoside, was isolated together with three known alkaloids, peimine, peiminine and ebeiensine from the fresh bulb of Fritillaria hupehensis Hsiao et K. C. Hsia. On the basis of the IR, 1H-NMR, 13C-MNR, FAB-MS and EI-MS of hupehemonoside, it has been established as 5 alpha, 14 alpha, 17 beta, 22 beta-cevanine-20 beta-hydroxyl-3 beta-O-beta-D-glucoside (IV).

Antitussive Agents↗
PubMed1991

[Time-lapse microcinematographical analysis of the biological characteristics of a macrophage-like cell line--MMC-1].

By using time-lapse microcinematography, we recorded and conducted an analysis of the macrophage-like cell line MMC-1, including observations of the spreading, polarity, contact inhibition and mitosis common to cultured cells as well as the properties of phagocytosis and rosette formation unique to macrophage. We also found an MMC-1 cell which, after feeding, still stretched its finger-like filopodia towards surrounding red blood cells. The filopodia extended as red blood cells moved towards them. At the point of contact, red blood cell fragments were seen moving towards the cell body along the filopodia; a kind of cytolysis was progressing.

Animals↗
PubMed1991

[Establishment of human adrenal gland and aldosterone-producing adenoma culture and the effect of alpha-human atrial natriuretic factor on aldosterone secretion in vitro].

Human adrenal gland and aldosterone-producing adenoma (APA) obtained from adrenalectomy could be maintained in vitro for one to two months. The explants continued to secrete aldosterone for the duration of culture. This method was superior to monolayer cell culture. The influence of alpha-human atrial natriuretic factor (alpha-hANF) was investigated by treating cultures of normal adrenal cortex and APA with alpha-hANF (10(-8) mol/L and 3 x 10(-8) mol/L respectively). We measured aldosterone in culture media collected at 2h before alpha-hANF treatment and 0.5, 2, 4 and 24h after. It was found that alpha-hANF stimulated aldosterone secretion of normal adrenal tissue but slightly inhibited that of APA.

Adenoma↗
PubMed1991

[Blood flow, CO2 response and autoregulation in the rat spinal cord by laser-Doppler flowmetry and hydrogen clearance].

Spinal cord blood flow (SCBF) was measured simultaneously by laser Doppler flowmetry (LDF) and hydrogen clearance (HC) in the normal Wistar rats. Under normal physiological condition, SCBF values by HC was 45.0 +/- 1.7 ml/min/100 g at the level of Th-8. LDF values were well correlated (r = 0.78) to the SCBF measured by HC, where linear regression line was obtained as y = 14.2x - 1.58. Absolute SCBF values of LDF were also calculated as 43.7 +/- 1.3 mg/min/100 g using this equation. CO2 response of SCBF were 1.09 ml/min/100 g/mmHg by HC and 1.01 ml/min/100 g by LDF, respectively. Autoregulation of SCBF maintained at a range of 55 -155 mmHg of mean arterial pressure in both methods. In conclusion, LDF is a useful technique for continuous SCBF monitoring. Since absolute SCBF value in LDF has some variance, the relative value is more suitable for accurate evaluation of SCBF during time course of an experiment.

Animals↗
PubMed1990

Effects of peptide hydrophobicity and charge state on molecular ion yields in plasma desorption mass spectrometry.

Plasma desorption mass spectra were obtained for a series of peptides, grouped in four mass ranges having approximately 9, 20, 30, and 40 amino acid residues. Within each group, the individual peptides differed in hydrophobicity, charge state, and retention time, as measured on a reversed-phase HPLC column. Comparison of the molecular ion intensities in the positive ion mass spectra of peptides from each group showed a strong dependence upon hydrophobicity and no correlation with charge state. Plasma desorption mass spectra of mixtures of all the peptides within each mass range generally resulted in the desorption of a single residue and suppression of the ion signal from other components. In most cases, this could be correlated with hydrophobicity, as calculated from the Bull and Breese index; however, a better correlation existed when the results were compared with reversed-phase retention times. In general the spectra of mixtures were not influenced by charge state (except in the absence of hydrophobic peptides), as the same component in each peptide mixture produced the most abundant ions in both positive and negative ion spectra.

Amino Acid Sequence↗
PubMed1990

Expression of mammalian DT-diaphorase in Escherichia coli: purification and characterization of the expressed protein.

A full-length cDNA clone, pKK-DTD4, complementary to rat liver cytosolic DT-diaphorase [NAD(P)H:quinone oxidoreductase (EC 1.6.99.2)] mRNA was expressed in Escherichia coli. The pKK-DTD4 cDNA was obtained by extending the 5'-end sequence of a rat liver DT-diaphorase cDNA clone, pDTD55, to include an ATG initiation codon and the NH2-terminal codons using polymerase chain reaction (PCR). Restriction sites for EcoRI and HindIII were incorporated at the 5'- and 3'-ends of the cDNA, respectively, by the PCR reaction. The resulting full-length cDNA was inserted into an expression vector, pKK2.7, at the EcoRI and HindIII restriction sites. E. coli strain AB1899 was transformed with the constructed expression plasmid, and DT-diaphorase was expressed under the control of the tac promotor. The expressed DT-diaphorase exhibited high activity of menadione reduction and was inhibited by dicumarol at a concentration of 10(-5)M. After purification by Cibacron Blue affinity chromatography, the expressed enzyme migrated as a single band on 12.5% sodium dodecyl sulfate-polyacrylamide gel with a molecular weight equivalent to that of the purified rat liver cytosolic DT-diaphorase. The purified expressed protein was recognized by polyclonal antibodies against rat liver DT-diaphorase on immunoblot analysis. It utilized either NADPH or NADH as electron donor at equal efficiency and displayed high activities in reduction of menadione, 1,4-benzoquinone, and 2,6-dichlorophenolindophenol which are typical substrates for DT-diaphorase. The expressed DT-diaphorase exhibited a typical flavoprotein spectrum with absorption peaks at 380 and 452 nm. Flavin content determination showed that it contained 2 mol of FAD per mole of the enzyme. Edman protein sequencing of the first 20 amino acid residues at the NH2 terminus of the expressed protein indicated that the expressed DT-diaphorase is not blocked at the NH2 terminus and has an alanine as the first amino acid. The remaining 19 amino acid residues at the NH2 terminus were identical with those of the DT-diaphorase purified from rat liver cytosol.

Amino Acid Sequence↗
PubMed1990

Circadian variations of serum sex hormone binding globulin binding capacity in normal adult men and women.

Diurnal variations of serum sex hormone binding globulin (SHBG), testosterone (T) and estradiol (E2) in five normal adult men and five normal adult women were investigated. SHBG binding capacity was measured by both polyacrylamide gel electrophoresis and dextran-coated charcoal technique (DCC); T and E2 were assayed by RIA and free T and free E2 were determined by means of equilibrium dialysis. In male subjects the variations of SHBG binding capacity was associated with the changes of total T, free T and T/SHBG index, which had the highest concentrations in the morning and the lowest levels in the evening during the 24 h test period, but percentage free T remained unchanged. Serum protein concentrations did not change significantly during 24 h. No significant diurnal changes of SHBG binding capacity, total E2, free E2, percentage free E2 and percentage free T were found in female subjects in the mid-luteal phase of the menstrual cycle, although significant fluctuations of total T, free T and T/SHBG index were observed throughout the day. The results suggested that SHBG may play a buffer role in the presence of fluctuations of testosterone production during 24 h period, allowing stabilization of a bioactive fraction of the hormone both in normal adult male and female. However, the concentrations of T in normal adult women may be too low to drive any change of SHBG levels while there were no significant variations of E2 throughout a day in the mid-luteal phase of the menstrual cycle.

Adult↗
PubMed1990

The metabolism of benzimidazole anthelmintics.

The benzimidazole carbamates are important broad-spectrum drugs for the control of helminth parasites in mammals. David Gottschall, Vassilios Theodorides and Richard Wang explain that the metabolism of these compounds depends heavily on the substituent present on carbon-5 of the benzimidazole nucleus and involves a wide variety of reactions. Work in vitro has shown that two major enzyme systems, the cytochrome P-450 family and the microsomal flavin monooxygenases are primarily responsible for these biotransformations. The parent compound is generally short-lived and its metabolites predominate in the tissues and excreta of treated animals. The metabolic pathways can be exploited therapeutically to overcome the problems of poor water solubility and adsorbtion of benzimidazoles by the development and use of more soluble prodrugs.

Journal Article↗
PubMed1990

Control of calcium channels in neuroblastoma cells (N1E-115).

Neuroblastoma cells (N1E-115) were used as models of transient (T) and long-lasting (L) Ca++ channels. The whole cell version of the patch clamp technique was used to measure inward Ca++ currents, and the fluorescent indicator, Fura-2, was used to measure changes in intracellular Ca++. Cells were cultured and selected during recording so that predominantly T or L channel currents were measured. T channel currents did not respond to dihydropyridine or parathyroid hormone, whereas L channel currents did. BAY-K-8644 increased and nifedipine decreased L channel currents. After a 15 mM KCl challenge, cells with predominantly T channels responded with a transient change in intracellular Ca++, while cells with predominantly L channels showed a sustained response. PTH inhibited the increase in intracellular Ca++ in cells with L channels, but not in those with T channels. PTH may be an example of an endogenous calcium channel blocker, at least in neuroblastoma cells.

Calcium Channel Blockers↗
PubMed1990

New refractive method for laser thermal keratoplasty with the Co:MgF2 laser.

We have observed corneal curvature changes from laser thermal keratoplasty with a Co:MgF2 laser. We studied corneal curvature changes in rabbits and have identified specific treatment patterns and laser parameters that can correct myopia and astigmatism. These corneal changes, some as large as 8 diopters, have been stable for at least one year, and slitlamp examination demonstrates clear central corneas with normal appearance.

Animals↗
PubMed1990

Specific inhibition of long-lasting, L-type calcium channels by synthetic parathyroid hormone.

The effect of an active synthetic N-terminal fragment of bovine parathyroid hormone (bPTH), bPTH-(1-34), on Ca2+ channels was studied in mouse neuroblastoma cells (N1E-115). With the whole-cell variation of the patch-clamp technique, T (transient) and L (long-lasting) types of Ca2+ currents were identified. Pharmacological characterization showed that the L current was amplified by the Ca2+ channel stimulator BAY K-8644, but the T current was unaffected. The administration of bPTH-(1-34) produced dose-related inhibition of the L current, which could be reversed by BAY K-8644. The peptide had no effect on the T current. In addition, use of the fluorescent indicator fura-2 showed that bPTH-(1-34) inhibited the KCl-stimulated increase in intracellular free Ca2+ in neuroblastoma cells with L channels but not in cells with T channels. An inactivated (oxidized) preparation of bPTH-(1-34) failed to affect the L current. High-affinity binding of labeled PTH analog to these neuroblastoma cells was also demonstrated. In addition, bPTH-(1-34) inhibited the L current in cultured vascular smooth muscle cells from rat tail artery. These data indicate that, in some tissues, PTH can act as an endogenous blocker of Ca2+ entry.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1990

hemofiltration reverses left ventricular dysfunction during sepsis in dogs.

Depressed left ventricular (LV) contractility in sepsis has been ascribed to the presence of circulating cardiodepressant substance (filterable cardiodepressant factor in sepsis [FCS]); however, this finding is controversial. The authors hypothesized that if a decrease in LV contractility indeed occurred due to a circulating depressant substance, then removal of this substance by hemofiltration would reverse by dysfunction. In this study, LV mechanics were examined before and after hemofiltration in anesthetized dogs during continuous intravenous infusion of live Escherichia coli. Left ventricular anterior-posterior and apex-base dimensions were measured by subendocardial ultrasonic crystal transducers implanted 4 weeks before the experiments. Left ventricular contractility was determined from the end-systolic pressure-dimension relationship. The slope of this relationship (Emax) is an index of contractility. After 4 h of sepsis, Emax was reduced by one half. Hemofiltration resulted in a return of Emax to control values. The FCS activity in the plasma was also assessed by the percent reduction in isometric contraction of electrically stimulated, isolated right ventricular trabeculae obtained from nonseptic dogs. The FCS activity reached a peak 4 h after sepsis and was reduced after 2 h of hemofiltration. The results show that during experimental sepsis, a circulating substance of less than 30,000 d produces a decrease in LV contractility and that this LV dysfunction may be improved by hemofiltration.

Animals↗
PubMed1990

Flunarizine selectively blocks transient calcium channel currents in N1E-115 cells.

The sensitivities of two types of voltage-dependent calcium channel currents in N1E-115 neuroblastoma cells to various agents were studied using the whole cell version of the patch clamp technique. Cells cultured in normal media expressed predominantly transient (T) currents whereas cells cultured in media with dimethylsulfoxide for 1 month expressed predominantly long-lasting (L) currents. Furthermore, by selecting cells with one or two short neurites it was possible to obtain cells which expressed only L channels. The dihydropyridine agonist, Bay K-8644 (5 microM), increased the amplitude of L channel currents by a factor of nearly two, whereas T channel currents were unaffected. Nifedipine (0.1 mM) significantly inhibited L channel currents, whereas T channel currents were insensitive to this treatment. Flunarizine, a diphenylpiperazine, had no effect on L channel currents but selectively inhibited T channel currents in a dose-dependent manner, with a significant effect at a concentration of 1 microM. However, flunarizine did not change the I-V relationships of T channel currents. Furthermore, the voltage dependence of T channel inactivation was shifted toward more negative potential by flunarizine. The present study provides direct evidence of the selective inhibition of T channel currents by flunarizine in N1E-115 neuroblastoma cells.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1990

[Synthesis of 2-formyl (acetyl) substituted quinoline thiosemicarbazones].

A series of 2-formyl (acetyl) substituted quinoline thiosemicarbazones (III, XII, XIII) were prepared in order to evaluate their antimalarial activity. Oxidation of substituted quinolines (IV) with selenium dioxide gave 2-formyl substituted quinolines (V). 2-Acetyl substituted quinoline (IX) was obtained from IV by oxidation, esterification, Claisen condensation and decarboxylation. III1-9 were synthesized by two methods; one was by condensation of 2-formyl (acetyl) substituted quinolines with methyl hydrazinecarbodithioat to form methyl-3-[1-(2-quinolinyl)-alkylidene] hydrazinecarbodithioate (XI), then the S-methyl group of XI was displaced by substituted amines to form the desired substituted thiosemicarbazones. The other was by condensation of 2-formyl (acetyl) substituted quinolines with 4-substituted-3-thiosemicarbazide (X) to afford directly III1-9, III10-12 were obtained by selective reduction of corresponding nitro compounds with stannous chloride and XII as a by-product was obtained by the nonselective reduction of III7 with stannous chloride. 3-Hexyl-4-oxothiazolin-2-yl(2-formyl or acetyl substituted quinoline) hydrazones (XIII1,2) were prepared from III1,4 via cyclization under sodium acetate condition. Eighteen compounds were found to be inactive in mice infected with ANKA strain of Plasmodium berghei.

Animals↗