Biomedical subjects

Qiong He

Publications and source records attributed to Qiong He.

9 recordsLinked to original sources

PubMed2007

Intracavity gain gratings.

Intracavity gain gratings are theoretically demonstrated to exhibit diffraction efficiencies that are 100 times larger than unity at pump powers substantially below the lasing threshold. Experiments performed using a Nd:YVO4 microlaser pumped below threshold by two interfering Ti:sapphire laser beams are described. Huge enhancement of the diffraction efficiency (5000X) and a large increase of the angular selectivity (10X) are demonstrated despite the angular reduction of the Fabry-Perot cavity finesse. Much better results are expected using gain gratings with larger areas or thinner cavities such as vertical cavity surface-emitting lasers. Such large fan-out values could be very interesting for applications to optical signal processing.

Journal Article↗

PubMed2006

Band-edge-induced Bragg diffraction in two-dimensional photonic crystals.

Two-dimensional photonic crystals composed of two orthogonal volume diffraction gratings have been photogenerated in photopolymers. When the read beam is set at the Bragg angle, the diffraction efficiency of the transmission grating is strongly enhanced at the band edge of the reflection grating recorded in the material. Such a device provides Bragg operation and enhancement of the diffraction efficiency of the thin diffraction grating together with good wavelength selectivity. Such advantages could be interesting for optical signal processing.

Journal Article↗

PubMed2006

Effects of replenishing qi, promoting blood circulation and resolving phlegm on vascular endothelial function and blood coagulation system in senile patients with hyperlipemia.

OBJECTIVE: To observe the curative effect of the method of replenishing qi, promoting blood circulation and resolving phlegm on senile hyperlipemia and its effects on vascular endothelial function and blood coagulation system. METHOD: 96 patients with senile hyperlipemia were randomly divided into a treatment group and a control group. 56 patients in the treatment group orally took danshen jueming granules while 40 patients in the control group orally took xuezhikang capsules. Observed were indexes of blood lipid, vascular endothelial function, blood coagulation system and safety. RESULTS: After treatment, the treatment group was obviously superior to the control group (P < 0.05) in reducing plasma total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) as well as in the ratio of thromboxane B2 (TXB2) to 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha), D-dimer (D-D) and fibrinogen (FIB). CONCLUSION: Danshen Jueming Granules have the effect of regulating metabolism of blood lipid, and improving vascular endothelial function and blood coagulation system in senile patients with hyperlipemia.

Aged↗

PubMed2005

Tetramethylpyrazine stimulates cystic fibrosis transmembrane conductance regulator-mediated anion secretion in distal colon of rodents.

AIM: To investigate the effect of tetramethylpyrazine (TMP), an active compound from Ligustium Wollichii Franchat, on electrolyte transport across the distal colon of rodents and the mechanism involved. METHODS: The short-circuit current (I(SC)) technique in conjunction with pharmacological agents and specific inhibitors were used in analyzing the electrolyte transport across the distal colon of rodents. The underlying cellular signaling mechanism was investigated by radioimmunoassay analysis (RIA) and a special mouse model of cystic fibrosis. RESULTS: TMP stimulated a concentration-dependent rise in I(SC), which was dependent on both Cl(-) and HCO(3)(-), and inhibited by apical application of diphenylamine-2,2'-dicarboxylic acid (DPC) and glibenclamide, but resistant to 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid disodium salt hydrate (DIDS). Removal of Na(+) from basolateral solution almost completely abolished the I(SC) response to TMP, but it was insensitive to apical Na(+) replacement or apical Na(+) channel blocker, amiloride. Pretreatment of colonic mucosa with BAPTA-AM, a membrane-permeable selective Ca(2+) chelator, did not significantly alter the TMP-induced I(SC). No additive effect of forskolin and 3-isobutyl-1-methylxanthine (IBMX) was observed on the TMP-induced I(SC), but it was significantly reduced by a protein kinase A inhibitor, H(89). RIA results showed that TMP (1 mmol/L) elicited a significant increase in cellular cAMP production, which was similar to that elicited by the adenylate cyclase activator, forskolin (10 micromol/L). The TMP-elicited I(SC) as well as forskolin- or IBMX-induced I(SC) were abolished in mice with homozygous mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) presenting defective CFTR functions and secretions. CONCLUSION: TMP may stimulate cAMP-dependent and CFTR-mediated Cl(-) and HCO(3)(-) secretion. This may have implications in the future development of alternative treatment for constipation.

Adrenergic beta-Agonists↗

PubMed2004

Differential Cl- and HCO3- mediated anion secretion by different colonic cell types in response to tetromethylpyrazine.

AIM: Colonic epithelium is known to secrete both Cl(-) and HCO(3)(-), but the secretory mechanisms of different colonic cell types are not fully understood. The present study aimed to investigate the differential activation of Cl(-) and HCO(3)(-) secretion by tetramethylpyrazine (TMP) in human crypt-like cell line, T84, and villus-like cell line, Caco-2, in comparison to the TMP-induced secretory response in freshly isolated rat colonic mucosa. METHODS: Colonic epithelial anion secretion was studied by using the short circuit current (I(SC)) technique. RT-PCR was used to examine the expression of Na(+)-HCO(3)(-)-cotranspoter in different epithelial cell types. RESULTS: TMP produced a concentration-dependent I(SC) which was increase in both T84 and Caco-2 cells. When extracellular Cl(-) was removed, TMP-induced I(SC) was abolished by 76.6% in T84 cells, but not in Caco-2 cells. However, after both Cl(-) and HCO(3)(-) were removed, TMP-induced I(SC) in Caco-2 cells was reduced to 10%. Bumetanide, an inhibitor of Na(+)-K(+)-Cl(-)-cotranspoter, inhibited the TMP-induced I(SC) by 96.7% in T84 cells, but only 47.9% in Caco-2 cells. In the presence of bumetanide and 4, 4'-diisothiocyanostilbene-2, 2'-disulfonic acid, an inhibitor of Na(+)-HCO(3)(-) cotransporter, inhibited the TMP-induced current in Caco-2 cells by 93.3%. In freshly isolated rat colonic mucosa, TMP stimulated distinct I(SC) responses similar to that observed in T84 and Caco-2 cells depending on the concentration used. RT-PCR revealed that the expression of Na(+)-HCO(3)(-) cotransporter in Caco-2 cells was 4-fold more greater than that in T84 cells. CONCLUSION: TMP exerts concentration-dependent differential effects on different colonic cell types with stimulation of predominant Cl(-) secretion by crypt cells at a lower concentration, but predominant HCO(3)(-) secretion by villus cells at a higher concentration, suggesting different roles of these cells in colonic Cl(-) and HCO(3)(-) secretion.

Animals↗

PubMed2004

The effect of cetyltrimethyl ammonium bromide on the electrochemical determination of thyroxine.

Electrochemical behavior of thyroxine at a polyvinylpyrrolidone modified carbon paste electrode in the presence of cetyltrimethyl ammonium bromide was described. Thyroxine underwent totally irreversible oxidation at this system and a well-defined peak at 0.42 V was obtained. The influence of various surfactants on the oxidation of thyroxine was examined by cyclic voltammetry. Chronocoulometry was also used to investigate the electrode process. In the range 2 x 10(-7) to 9 x 10(-6)mol/l, the thyroxine concentration was linear with the oxidation peak current and a low detection limit of 8 x 10(-8) mol/l was obtained for 5 min accumulation.

Calibration↗

PubMed2004

Enhanced reduction and determination of trace thyroxine at carbon paste electrode in the presence of trace cetyltrimethylammonium bromide.

The electrochemical response of thyroxine (T4) at a carbon paste electrode (CPE) in the presence of cetyltrimethylammonium bromide (CTAB) was investigated. It gave a well-defined oxidation peak at 0.80 V and a sensitive reduction peak at 0.40 V. Compared with the indiscernible signal in the absence of CTAB, the reduction current of T4 at CPE was greatly enhanced in the presence of CTAB, due to the interactions between T4, CTAB and the hydrophobic electrode surface. The electrode process of T4 was explored by cyclic voltammetry and chronocoulometry. The effect of surfactants on the reduction reaction proved that bromide ions (Br(-)) in CTAB might form special ion complexes with T4 via a special interaction with the iodine atoms on T4, which would activate the reduction of T4. The sensitive and selective reduction of T4 in this system was applied to the determination of T4 in drugs; a detection limit of 6.5 x 10(-9) M was obtained (sigma= 3).

Bromides↗

PubMed2003

Basolateral membrane mechanisms involved in ligustrazine-stimulated anion secretion in rat distal colon.

The present study investigated the cellular mechanism underlying the effect of ligustrazine on the ion transport in rat distal colon using the short-circuit current (I(SC)) technique. In freshly isolated colonic strips, basolateral addition of ligustrazine stimulated a rise in I(SC), which was resistant to basolateral application of neuronal sodium channel blocker tetrodotoxin (TTX), but inhibited by 55.2% by basolateral pretreatment with prostaglandin inhibitor indomethacin. The ligustrazine-induced I(SC) increase was inhibited by apical application of Cl(-) channel blockers diphenylamine-2,2'-dicarboxylic acid (DPC) and glibenclamide. Basolaterally administered bumetanide, an inhibitor of Na(+)-K(+)-2 Cl(-) cotransporter, inhibited ligustrazine-evoked current increases by 85.2% and basolateral exposure to Ba(2+), a non-specific potassium channels blocker, and blocked the current by more than 90%, indicating that basolateral Na(+)-K(+)-2 Cl(-) cotransporter and K(+) channels played an important role in the effect of ligustrazine. The results suggested that ligustrazine could stimulate rat distal colon (-) secretion that is mediated by basolateral Na(+)-K(+)-2 Cl(-) cotransporter and K(+) channel.

Animals↗

PubMed2003

Voltammetric method based on an ion-pairing reaction for the determination of trace amount of iodide at carbon-paste electrodes.

Carbon-paste electrodes (CPEs) were studied to elucidate the cathodic stripping voltammetric determination of iodine. At an accumulation potential of 1.0 V (vs. SCE), iodide was preconcentrated on CPEs via an ion-pairing reaction, followed by oxidation to iodine. Then a linear scan voltammogram was recorded after 10 s of quiescent time by a cathodic potential scan from 0.7 V to 0.1 V at a scan rate of 100 mV s(-1). A cathodic peak current was obtained at about 0.38 V. Various experiment parameters such as the acidity, chloride concentration, accumulation potential, accumulation time, concentration of cetyltrimethylammonium bromide (CTAB) and scan rate, were optimized to analyze the iodide by employing linear-scan stripping voltammetry. Under the optimal conditions, calibration curves were obtained over a wide concentration range of the iodide ion from 8 x 10(-9) mol L(-1) to 5 x 10(-6) mol L(-1) with a detection limit of 2 x 10(-9) mol L(-1) at an accumulation time of 3 min. The effect of interfering species was evaluated and the procedure was applied to an iodide analysis in table salt, with good results.

Journal Article↗