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Biomedical subjects

Z L Chen

Publications and source records attributed to Z L Chen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Hot electrons in the interaction of femtosecond laser pulses with foil targets at a moderate laser intensity.

Characteristics of hot electrons produced in the interaction of femtosecond laser pulses with foil targets were investigated at a moderate laser intensity. Both outgoing and ingoing hot electrons from the femtosecond laser plasma were studied. A collimated jet of outgoing hot electrons was observed in the target normal direction. An ingoing energetic hot-electron beam was found in the laser propagation direction, while the low-energy ingoing electrons spread into wider cone angle due to the collisional effects in the plasma and target material. These observations were supported by three-dimensional Monte Carlo simulations. The hot-electron temperature obtained from electron spectra and absorption experiments implies that resonance absorption is partially responsible for the generation of hot electrons.

Journal Article↗
PubMed2001

Reactive oxygen species involved in trichosanthin-induced apoptosis of human choriocarcinoma cells.

The type-I ribosome-inactivating protein trichosanthin (TCS) has a broad spectrum of biological and pharmacological activities, including abortifacient, anti-tumour and anti-HIV activities. We have found for the first time that TCS stimulated the production of reactive oxygen species (ROS) in JAR cells (a human choriocarcinoma cell line) in a time- and concentration-dependent manner by using the fluorescent probe 2',7'-dichlorofluorescein diacetate with confocal laser scanning microscopy. ESR spectral studies and the inhibition of ROS formation by the superoxide radical anion (O(2)(-.)) scavenger superoxide dismutase, the H(2)O(2) scavenger catalase and the hydroxyl radical (OH(.)) scavenger mannitol suggested the involvement of O(2)(-.), H(2)O(2) and OH(.). TCS-induced ROS formation was shown to be dependent on the presence of both extracellular and intracellular Ca(2+); moreover, ROS production paralleled the intracellular Ca(2+) elevation induced by TCS, suggesting that ROS production might be a consequence of Ca(2+) signalling. TCS-induced activation of caspase-3 was initiated within 2 h; however, TCS-induced production of ROS was initiated within 5 min, suggesting that the production of ROS preceded the activation of caspase-3. Simultaneous observation of the nuclear morphological changes via two-photon laser scanning microscopy and ROS production via confocal laser scanning microscopy revealed that ROS is involved in the apoptosis of JAR cells. The involvement of ROS was also confirmed by the inhibition of TCS-induced cell death by the antioxidant Trolox and the ROS scavengers catalase and mannitol. Diethylenetriaminepenta-acetic acid, an inhibitor of metal-facilitated OH(.) formation, markedly inhibited TCS-induced cell death, suggesting that TCS induced OH(.) formation via the Fenton reaction. The finding that ROS is involved in the TCS-induced apoptosis of JAR cells might provide new insight into the anti-tumour and anti-HIV mechanism of TCS.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Experimental study of a subpicosecond pulse laser interacting with metallic and dielectric targets.

We have studied laser absorption, hot electron emission, and the energy spectrum of hot electrons produced during the interaction of a 150 fs, 5 mJ, 800 nm p-polarized laser pulse at 8x10(15) W/cm(2) with metallic and dielectric target materials. Because dielectric targets are much less conductive, the charge separation potential in dielectric targets is higher than that of metallic targets. This leads to a smaller laser absorption, fewer emitted electrons, and a lower hot electron temperature in dielectric than in metallic targets.

Journal Article↗
PubMed2001

Benzopyran derivatives from Mallotus apelta.

From the leaves of Mallotus apelta, seven benzopyran compounds were obtained and their structures were determined using spectroscopic methods. One showed moderate antibiotic activity against Micrococcus lutens.

Benzopyrans↗
PubMed2001

Three new hyperforin analogues from Hypericum perforatum.

Three new analogues of hyperforin (1), pyrano[7,28-b]hyperforin (2), (2R,3R,4S,6R)-6-methoxycarbonyl-3-methyl-4,6-di(3-methyl-2-butenyl)-2-(2-methyl-1-oxopropyl)-3-(4-methyl-3-pentenyl)cyclohexanone (3), and (2R,3R,4S,6S)-3-methyl-4,6-di(3-methyl-2-butenyl)-2-(2-methyl-1-oxopropyl)-3-(4-methyl-3-pentenyl)cyclohexanone (4), were isolated from the aerial parts of Hypericum perforatum (St. John's wort). The structures of 2-4 were elucidated by spectroscopic methods.

Anti-Bacterial Agents↗
PubMed2001

Pharmacokinetics of sarafloxacin in pigs and broilers following intravenous, intramuscular, and oral single-dose applications.

Pharmacokinetics of sarafloxacin, a fluoroquinolone antibiotic, was determined in pigs and broilers after intravenous (i.v.), intramuscular (i.m.), or oral (p.o.) administration at a single dose of 5 (pigs) or 10 mg/kg (broilers). Plasma concentration profiles were analysed by a noncompartmental pharmacokinetic method. Following i.v., i.m. and p.o. doses, the elimination half-lives (t1/2beta) were 3.37 +/- 0.46, 4.66 +/- 1.34, 7.20 +/- 1.92 (pigs) and 2.53 +/- 0.82, 6.81 +/- 2.04, 3.89 +/- 1.19 h (broilers), respectively. After i.m. and p.o. doses, bioavailabilities (F) were 81.8 +/- 9.8 and 42.6 +/- 8.2% (pigs) and 72.1 +/- 8.1 and 59.6 +/- 13.8% (broilers), respectively. Steady-state distribution volumes (Vd(ss)) of 1.92 +/- 0.27 and 3.40 +/- 1.26 L/kg and total body clearances (ClB) of 0.51 +/- 0.03 and 1.20 +/- 0.20 L/kg/h were determined in pigs and broilers, respectively. Areas under the curve (AUC), mean residence times (MRT), and mean absorption times (MAT) were also determined. Sarafloxacin was demonstrated to be more rapidly absorbed, more extensively distributed, and more quickly eliminated in broilers than in pigs. Based on the single-dose pharmacokinetic parameters determined, multiple dosage regimens were recommended as: a dosage of 10 mg/kg given intramuscularly every 12 h in pigs, or administered orally every 8 h in broilers, can maintain effective plasma concentrations with bacteria infections, in which MIC90 are <0.25 microg/mL.

Administration, Oral↗
PubMed2001

Gastrodianin-like mannose-binding proteins: a novel class of plant proteins with antifungal properties.

The orchid Gastrodia elata depends on the fungus Armillaria mellea to complete its life cycle. In the interaction, fungal hyphae penetrate older, nutritive corms but not newly formed corms. From these corms, a protein fraction with in vitro activity against plant-pathogenic fungi has previously been purified. Here, the sequence of gastrodianin, the main constituent of the antifungal fraction, is reported. Four isoforms that encoded two different mature proteins were identified at the cDNA level. Another isoform was detected in sequenced peptides. Because the antifungal activity of gastrodianins produced in and purified from Escherichia coli and Nicotiana tabacum was comparable to that of gastrodianin purified from the orchid, gastrodianins are the active component of the antifungal fractions. Gastrodianin accumulation is probably an important part of the mechanism by which the orchid controls Armillaria penetration. Gastrodianin was found to be homologous to monomeric mannose-binding proteins of other orchids, of which at least one (Epipactis helleborine mannose-binding protein) also displayed in vitro antifungal activity. This establishes the gastrodianin-like proteins (GLIPs) as a novel class of antifungal proteins.

Amino Acid Sequence↗
PubMed2001

[Continuously perfused cultivation of genetically-engineered CHO cells producing prothrombin in a modified Super-Spinner].

A Super-Spinner was Modified by mounting a stainless steel filter(pore size 75 microns) to the impeller shaft to retain cells while fresh nutrient is perfused. Using Macroporous microcarrier Cytopore 1, continuously perfused cultivation of a recombinant CHO cell line, CHO2DS producing prothrombin was performed with the perfusion of a protein-free medium DF6S. The cell retention rate was more than 90% during the 24 days continuously perfused cultivation. The viable cell density of CHO2DS and prothrombin concentration reached 4.62 x 10(6)(cells.m/L) and 11.3(mg/L) respectively after 9 days culture.

Animals↗
PubMed2001

[The tissue culture of medicinal plant Trichosanthes kirilowii and its protein analysis].

We reported preliminary results of rapid propagation, callus induction and regeneration of Trichosanthes Kirilowii, and its protein analysis. Pre-existing meristerms regenerate shoots very rapidly when grown on MS medium containing 0.5 or 1.0 mg/L 6-BA; calli could be induced from leaf sections when put on MS medium containing 4.0 mg/L 6-BA + 0.2 mg/L IAA; shoots regenerated successfully 30 days after calli induction and the differentiation ratio was one shoot out of every four leaf sections; and all shoots gave rise to roots after removing onto MS medium containing 0.1 mg/L NAA and 100% survived when transplanted into soil. Very excitingly, these plants produced small tubers in one month, where satisfactory expression of TCS protein was detected by Western blot analysis.

Culture Media↗
PubMed2001

Pharmacokinetics of lactosaminated recombinant human growth hormone in mice.

AIM: To study the pharmacokinetic characteristics of lactosaminated recombinant human growth hormone (hGH-L) in mice. METHODS: The biodistribution was studied with in vivo radioactive tracer technique. The pharmacokinetics was investigated by radioimmunoassay (RIA) method of hGH-L. The results were compared with that of recombinant human growth hormone (hGH). RESULTS: 125I-hGH-L has remarkable livertaxis. The area under drug concentration-time curve (32686.9 microg . min . L-1) in blood and serum mean residence time (21.4 min) of hGH-L are less than that of hGH (36913.1 microg . min . L-1 and 24.9 min) (P < 0.05). In target organ liver, hGH-L distribution half life (1.8 min) and elimination half life (11.1 min) are shorter than that of hGH (2.1 min and 27.7 min) (P < 0.05). The area under drug concentration-time curve (17621.9 microg . min . L-1) of hGH-L is bigger than that of hGH(12148.2 microg . min . L-1) (P < 0.05) in liver. CONCLUSION: The pharmacokinetic parameters of hGH-L has obvious advantage over that of hGH.

Amino Sugars↗
PubMed2001

[Simultaneous determination of chlorpheniramine, paracetamol and pseudo-ephedrine hydrochloride in composite tablets by high performance liquid chromatography].

An HPLC method is described for the determination of chlorpheniramine, paracetamol and pseudoephedrine hydrochloride simultaneously in Nuonuo composite tablets. Chromatographic conditions were: column, YWG-C18 column (150 mm x 4.0 mm i.d., 10 microns); mobile phase, 25% methanol(0.05 mol/L sodium dihydrogen phosphate); flow rate, 1.0 mL/min; detection wavelength, 205 nm; injection volume, 20 microL. The detection limits of chlorpheniramine, paracetamol and pseudo-ephedrine hydrochloride were 1.16 mg/L, 0.15 mg/L and 1.82 mg/L respectively and the corresponding average recoveries were 98.35% (n = 5, RSD = 1.60%), 101.16% (n = 5, RSD = 1.50%) and 98.50% (n = 5, RSD = 1.59%) respectively. The proposed method is simple, rapid and accurate and has been satisfactorily used for the quantitative analysis of real samples.

Acetaminophen↗
PubMed2000

Coumarinolignoids of Mallotus apelta.

Three coumarino-lignoids, aquillochin (1), cleomiscosin A and 5'-demethylaquillochin have been isolated from Mallotus apelta. The structure of the new compound 3 was determined by spectroscopic techniques.

Coumarins↗
PubMed2000

Electrophysiological effects of protopine in cardiac myocytes: inhibition of multiple cation channel currents.

Protopine (Pro) from Corydalis tubers has been shown to have multiple actions on cardiovascular system, including anti-arrhythmic, anti-hypertensive and negative inotropic effects. Although it was thought that Pro exerts its actions through blocking Ca(2+) currents, the electrophysiological profile of Pro is unclear. The aim of this study is to elucidate the ionic mechanisms of Pro effects in the heart. In single isolated ventricular myocytes from guinea-pig, extracellular application of Pro markedly and reversibly abbreviates action potential duration, and decreases the rate of upstroke (dV/dt)(max), amplitude and overshoot of action potential in a dose-dependent manner. Additionally, it produces a slight, but significant hyperpolarization of the resting membrane potential. Pro at 25, 50 and 100 microM reduces L-type Ca(2+) current (I(Ca,L)) amplitude to 89.1, 61.9 and 45.8% of control, respectively, and significantly slows the decay kinetics of I(Ca,L) at higher concentration. The steady state inactivation of I(Ca,L) is shifted negatively by 5.9 - 7.0 mV (at 50 - 100 microM Pro), whereas the voltage-dependent activation of I(Ca,L) remains unchanged. In contrast, Pro at 100 microM has no evident effects on T-type Ca(2+) current (I(Ca,T)). In the presence of Pro, both the inward rectifier (I(K1)) and delayed rectifier (I(K)) potassium currents are variably inhibited, depending on Pro concentrations. Sodium current (I(Na)), recorded in low [Na(+)](o) (40 mM) solution, is more potently suppressed by Pro. At 25 microM, Pro significantly attenuated I(Na) at most of the test voltages (-60 approximately +40 mV, with a 53% reduction at -30 mV. Thus, Pro is not a selective Ca(2+) channel antagonist. Rather, it acts as a promiscuous inhibitor of cation channel currents including I(Ca,L), I(K), I(K1) as well as I(Na). These findings may provide some mechanistic explanations for the therapeutic actions of Pro in the heart.

Action Potentials↗
PubMed2000

New products from alkali fusion of ginkgolides A and B.

Alkali fusion of ginkgolides A and B has afforded five unexpected products 3-7. Their structures were established from their spectral data and chemical reactions. They were evaluated for their in vitro activity to inhibit the platelet-activating factor-induced aggregation of rabbit platelets and show less potency than ginkgolides A and B.

Animals↗
PubMed2000

Three new triterpenoid saponins from the seeds of Vaccaria segetalis.

Three new triterpenoid saponins, named segetoside G(1), H(2) and I(3), have been isolated from the seeds of Vaccaria segetalis. On the basis of chemical reaction and spectral data, their structures have been established as: 28-O-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-arabinofuranosyl (1-->3)]-beta-D-(4-O-acetyl)-fucopyranosyl-gypsogenin-3-O-beta-D-galactopyranosyl-(1-->2)-beta-D-(6-O-butyl ester)-glucuronopyranoside (1), 28-O-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-(5-O-acetyl)-arabinofuranosyl-(1-->3)]-beta-D-(4-O-acetyl)-fucopyranosyl-gypsogenin-3-O-beta-D-galactopyranosyl-(1-->2)-beta-D-glucuronopyranoside (2) and 28-O-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-(5-O-acetyl)-arabinofuranosyl-(1-->3)]-beta-D-(4-O-acetyl)-fucopyranosyl-quillaic acid-3-O-beta-D-galactopyranosyl-(1-->2)-beta-D-glucuronopyranoside (3).

China↗
PubMed2000

Right ventricular and septal anomalies complicated by subacute bacterial endocarditis.

We report the case of a 31-year-old woman with no history of heart disease. She came to the hospital with fever, dyspnea, palpitation, and edema of the lower extremities. She was found to have aortic, mitral, and pulmonary valve insufficiency, and the initial diagnosis was subacute bacterial endocarditis. At surgery, we replaced the aortic and mitral valves with mechanical prostheses and the pulmonary valve with a bioprosthesis. The prostheses were soaked intraoperatively with fluconazole and the heart chambers were irrigated with povidone-iodine to prevent infection by bacteria and fungi. We also found 2 previously unsuspected anomalies: 1 was a muscular bundle that divided the right ventricle into 2 chambers, and the other was a ventricular septal defect, 1.0 cm in diameter. We resected the muscular bundle and patched the septal defect. The patient had an uneventful postoperative course and was in New York Heart Association functional class I at the 15-month follow-up visit. We speculate that this patient's congenital anomalies made the heart more susceptible to damage from the endocarditis. Therefore, any patient who has infective endocarditis should also be examined closely for congenital defects.

Adult↗