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Biomedical subjects

S Z Yao

Publications and source records attributed to S Z Yao.

At least 19 recordsLinked to original sources
PubMed2002

Immunosensor for the differentiation and detection of Salmonella species based on a quartz crystal microbalance.

Immunosensors based on the microgravimetric quartz crystal microbalance (QCM) technique have been developed for the detection of Salmonella species from serogroups A, B and D. Salmonella serogroup-specific murine monoclonal antibodies, respectively, raised against these serogroups were immobilized onto the silver electrodes of piezoelectric (PZ) crystals by cross-linkage via glutaraldehyde (GA) to the electrode surfaces pre-coated with thin polyethyleneimine (PEI) layer. The specific immunosensors developed gave responses in linear ranges from 10(5) to 5x10(8) cells per ml with no significant interference from other strains of Salmonella and Escherichia coli up to 10(8) cells per ml. They showed good repeatability and excellent linear range, achieving detection limits down to 10(4) cells per ml with ability to distinguish different strains of Salmonella. These biosensors exhibited an exquisite specificity evidenced by their ability to discriminate antigens, the structures of which differ only by the isomeric form of di-deoxyhexose. The antibody-modified crystals showed no loss in activity over 4 days under storage at 4 degrees C.

Animals↗
PubMed2001

Ion chromatographic determination of calcium and magnesium cations in human saliva and urine with a piezoelectric detector.

In this present paper, simultaneous determination of Ca(2+) and Mg(2+) cations in saliva, urine was achieved using an ion chromatography method, in which a piezoelectric quartz crystal (PQC) sensor was used as a detector, and a solution containing tartaric acid (4 mmol 1(-1)) and ethylenediamine (2 mmol 1(-1)) as a mobile phase. Good linearities were obtained over the ranges of 0.8-500 mg 1(-1) Ca(2+) and 1.0-500 mg 1(-1) Mg(2+). The detection limits were 0.4 mg 1(-1) for Ca and 0.2 mg 1(-1) for Mg, respectively.

Calcium↗
PubMed2001

Simultaneous determination of nitrate and nitrite in saliva and foodstuffs by non-suppressed ion chromatography with bulk acoustic wave detector.

In the present paper, nitrate and nitrite in foodstuffs and saliva were simultaneously determined using a non-suppressed ion chromatography (IC) method with a bulk acoustic wave sensor (BAW) as detector, and 1.5 mmol/L potassium hydrogenphthalate (KHP) as mobile phase. The IC-BAW method is simple, rapid and accurate. The determination limits for nitrite and nitrate are 0.20 and 0.30 mg/L, respectively. The IC-BAW is comparable and agrees with the conventional spectrophotometric method for nitrite and nitrate determination.

Chromatography, Ion Exchange↗
PubMed2000

Determination of divalent carboxylic acids in traditional Chinese herbal and patent medicines using HPLC with double cell quartz crystal detector.

A rapid, simple and sensitive high performance liquid chromatography (HPLC) method combined with a novel double cell quartz crystal (DCQC) detector is described for the determination of divalent carboxylic acids in traditional Chinese herbal and patent medicines. The chromatographic system involves the use of a muBondapak-NH2 column with 20 mM KH2PO4 (pH 3.4, adjusted by H3PO4)/acetonitrile (95:5%) as a mobile phase. The DCQC detector has a low temperature coefficient and high conductance sensitivity independent of the background from 7.2 to 2500 microS. Analysis of sample is completed without the use of an ion suppression device.

Calibration↗
PubMed2000

Determination of the binding parameters of drug to protein by equilibrium dialysis/piezoelectric quartz crystal sensor.

A novel method, equilibrium dialysis/piezoelectric quartz crystal sensor, applied to determine the binding parameters of diethyldithiocarbamate to human plasma protein is proposed. Based on the investigation of the equilibrium reaction for the binding of drug to protein, the related theoretical equations for this binding were derived. By monitoring the frequency responses of a copper-plated piezoelectric quartz crystal sensor to drug in and out of a dialysis membrane after equilibrium, the binding parameters were determined, i.e., 0.375 micromol g(-1) for beta(p), 6.496 microM for K(dp), 141.99 L mmol(-1) for K(p), and 0.043 for N. These values were in good agreement with reference values. It was found that this method may have application for studying the characteristics of the interaction between other drugs and proteins.

Biosensing Techniques↗
PubMed1998

Flow-injection determination of total ammonia and total carbon dioxide in blood based on gas-diffusion separation and with a bulk acoustic wave impedance sensor.

A novel flow-injection (FIA) system, for the rapid and direct determination of both total ammonia (T[NH3]) and total carbon dioxide (T[CO2]) in clinical blood samples, has been developed. Samples were injected into a carrier stream of H2O, then emerged with a reagent stream, where the analyte was converted into a gaseous species and diffused across a PTFE gas-permeable membrane into an acceptor stream. The trapped NH3/CO2 in the acceptor was determined on line by a bulk acoustic wave (BAW) impedance sensor. At a through-put of 20 and 65 h(-1), the proposed system exhibited a linear frequency response up to 200 micromol l(-1) ammonium and 20 mmol l(-1) bicarbonate with a detection limit of 1.0 and 10 micromol l(-1), respectively. Results obtained for T(NH3) in serum and T(CO2) in plasma were in agreement with those obtained by the conventional glutamate dehydrogenase (GDH) method and gas-sensing electrode method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rate and potential interferents on the FIA signals were also discussed.

Acoustics↗
PubMed1997

Ion chromatographic study of sodium, potassium and ammonium in human body fluids with bulk acoustic wave detection.

In the present paper, determination of Na+, K+ and NH4+ in saliva and serum was carried out using an ion chromatography (IC) method with a bulk acoustic wave (BAW) sensor as detector and 2.0 mmol/l nitric acid as mobile phase. The IC-BAW method is simple, rapid and accurate. Comparison between the BAW detector and the conventional conductivity detector (CDD) was discussed. The IC-BAW showed agreement with the commonly used flame photometric method for Na+ and K+ and enzymatic method for NH4+, as well as IC-CDD for those three cations.

Body Fluids↗
PubMed1996

Bulk acoustic wave sensor for investigating hemorheological characteristics of plasma and its coagulation.

A method of using a bulk acoustic wave (BAW) device to study the hemorheological phenomena is proposed. By measuring the resonant resistance of a BAW device, the dependence of the plasma viscosity on its composition is investigated. It has been found that during the process of the plasma coagulation, the frequency response of a BAW device is dominated by the change in plasma viscoelasticity, and useful information such as the coagulation time and the viscoelasticity of coagulated plasma can be obtained from the curve of frequency response. Based on the BAW quartz detection system, effects of fibrinogen, thrombin and some drugs on the plasma coagulation are investigated. The results show that the BAW device based on the oscillator method possesses some advantages, such as high sensitivity, simplicity of use, cost effectiveness and small sample volume for clinical hemorheological study.

Acoustics↗
PubMed1996

Determination of dipyridamole by modified extraction-gravimetry with a surface acoustic wave resonator sensor.

A simple and sensitive extraction-gravimetric method for the determination of dipyridamole is presented. The method is based on the extraction of free dipyridamole with chloroform, after neutralization with a basic agent, followed by measurement of the frequency shift response of the specially designed surface acoustic wave resonator sensor after evaporation of the extractant from the surface of the resonator. The frequency shift response was proportional to the amount of dipyridamole in the range 0.065-1.12 micrograms. Experimental parameters and the effect of interfering substances on the assay of dipyridamole were also examined in this study. The method was applied to the determination of dipyridamole in tablets.

Chloroform↗
PubMed1995

Determination of lactic acid and pyruvic acid in serum and cerebrospinal fluid by ion-exclusion chromatography with a bulk acoustic wave detector.

A chromatographic method base don a combination of ion-exclusion chromatography separation and bulk acoustic wave series piezoelectric quartz crystal detector quantification for the determination of pyruvic acid and lactic acid in serum and cerebrospinal fluid (CSF) was developed. The separation was carried out using a Shim-pak SCR-102H ion-exclusion column with phosphoric acid solution as eluent. The method shows an acceptable detection limit and anti-interference ability. Serum and CSF from healthy individuals and patient were analysed successfully.

Acoustics↗
PubMed1995

Application of a series piezoelectric sensor as a detector in ion chromatography.

The application of a series piezoelectric sensor as a detector for ion chromatography (IC) is investigated. The device is used with sensitive response between the series piezoelectric quartz crystal oscillation frequency and specific conductivity of liquids for ion chromatographic detection. Two platinum wires are used as conductivity electrodes and inserted oppositely in the detection cell. The dead-volume of the detection is 15 microL, the noise is less than or equal to 1 Hz, the baseline drift is 5 Hz/h, and the detection limits of F- and Na+ are 5 and 25 ng, respectively. The effects of temperature, background conductivity, cell constant of the conductivity electrode, and dead volume on the sensitivity of the detector are discussed. The detector temperature should equal that of the column. An optimum sensitivity is obtained when the cell constant is approximately 3.5 cm. The optimum range of the background conductivity of the mobile phase is 150 to 1200 microseconds. When the solution conductivity is greater than 3000 microseconds, the detector does not work satisfactorily. The proposed IC cerebrospinal fluid detection method is applied to the determination of vitamin C in apple and Zn2+, Ca2+, Mg2+, and Cu2+ in human cerebrospinal fluid.

Ascorbic Acid↗
PubMed1995

Endocrine consequences of prenatal sodium depletion prepare rats for high need-free NaCl intake in adulthood.

Offspring of dams that were repeatedly sodium depleted during late pregnancy (at days E14, E17, and E20) expressed high need-free 3% NaCl intake in adulthood. Need-free 3% NaCl intake was greater in females, thereby respecting the sexual dimorphism of this behavior, and was increased further by successive sodium depletion in adulthood. Offspring from dams that had been sodium depleted while receiving the angiotensin-converting enzyme inhibitor, captopril, showed a need-free NaCl intake similar to that of control rats nonneonatally sodium depleted. Trunk blood taken from dams at day E18, i.e., 24 h after the second treatment, revealed that sodium depletion produced marked increases in the dam's plasma angiotensin (ANG) II and aldosterone that were not present when dams were treated with captopril during sodium depletion, even though both groups displayed a similar hyponatremia. We therefore propose that, during prenatal sodium depletion, the activation of the angiotensin-aldosterone system rather than the loss of sodium itself is responsible for the modification in need-free NaCl intake behavior. Finally, we suggest that, during pregnancy, ANG II may have an organizational effect on the neural substrate in the fetal brain that subserves subsequent NaCl intake behavior.

Aging↗
PubMed1994

[Effect of angiotensin on salt intake behavior of rat].

Intravenous infusion of various doses of Ang II caused significant increases of the salt intake in S-D rats as a result of natriuretic action of the drug. The phenomenon could be abolished by administration of aldosterone but unaffected by adrenalectomy. Captopril could suppress the Ang II effect. Discrepancies with a previous work on the interpretation of the action mode of Ang II were discussed.

Adrenalectomy↗
PubMed1993

Reaction-frequencymetric method: a new analytical technique for determination of submicromolar concentration levels of vitamin C.

A new analytical technique for the assay of pharmaceutical substances at low concentration levels has been proposed and applied to the determination of vitamin C as an example of its application. It is based on the chemical reaction of vitamin C with iodine in a sodium citrate-hydrochloric acid medium, followed by measurement of the frequency change of a silver-plated piezoelectric quartz crystal. The frequency change is proportional to the vitamin C concentration from 2 x 10(-7) to 4 x 10(-6) M. The method was applied to the assay of vitamin C in pharmaceutical preparations.

Ascorbic Acid↗
PubMed1993

[Simultaneous determination of vitamin B1 and vitamin C in aqueous solution with piezoelectric crystal quartz sensors].

According to the response properties of piezoelectric crystal quartz sensors to the solution conductivity the frequency shift response was derived to show a linear dependence on the concentrations of vitamin B1 (VB1) and vitamin C (VC). This was experimentally verified and a calibration model for simultaneous determinations of the two vitamins was established. The usefulness of the technique was evaluated by quantitation of mixtures of unknown composition using common multiple linear regression (MLR) and partial least squares (PLS). The average relative standard deviations for six samples were 4.46% for VB1 and 6.63% for VC with MLR; and 1.97% for VB1 and 2.74% for VC with PLS, respectively.

Ascorbic Acid↗
PubMed1992

The anteroventral wall of the third ventricle and the angiotensinergic component of need-induced sodium intake in the rat.

Because the anteroventral wall of the third ventricle (AV3V) has been implicated in the control of sodium intake it was studied in rats with damage of the AV3V region in the sodium-replete and sodium-deplete states, and when they were treated with either pulse intracerebroventricular (pICV) injection of renin to activate brain angiotensin or daily subcutaneous injections of deoxycorticosterone (DOCA). The response of rats with AV3V damage to sodium depletion was retarded and the excess sodium intake that is induced by pICV renin was absent, but their daily need-free sodium intake and the sodium intake that is induced by DOCA were essentially normal. The results suggest that the AV3V is responsible for the angiotensinergic, but not the aldosteronergic, component of the ANG II/ALDO synergy that controls need-induced sodium appetite in the rat. The integrity of the AV3V is not necessary for daily need-free sodium intake or for its enhancement by sodium depletions, suggesting that ANG II is probably not important for these phenomena. But ANG II action within the AV3V might be important for the rapid burst of sodium intake that immediately follows a period of depletion.

Aldosterone↗
PubMed1992

Deficits in NaCl ingestion after damage to the central nucleus of the amygdala in the rat.

These studies examined the NaCl intake behaviors of rats with bilateral electrolytic lesions of the central nucleus of the amygdala (CeAX). Daily need-free intake of 3% NaCl was abolished by CeAX even in rats in which it had been enhanced preoperatively by a history of repeated sodium depletions but was slightly restored by three successive postoperative sodium depletions. CeAX rats drank water but not 3% NaCl to high doses of DOCA and to the activation of cerebral angiotensin II, and expressed small but reliable salt intake (need-induced salt intake or salt appetite) after postoperative sodium depletions. Other ingestive behaviors (water drinking, intake of food and 5% sucrose) were normal. When given decreasing concentrations of NaCl solution the CeAX rats rejected them until the concentration reached 0.2%. These findings suggest that lesions to the central nucleus of the amygdala produce a global impairment in salt intake behaviors that is possibly due to an alteration in the central processing of the salt taste signal.

Amygdala↗