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Biomedical subjects

Q Zhang

Publications and source records attributed to Q Zhang.

At least 307 records · Page 17Linked to original sources
PubMed2000

Synthesis and characteristics of the human serum albumin-triazine chiral stationary phase.

Human serum albumin (HSA) was successfully bonded to silica with s-triazine as activator. The coupling reaction by this method was rapid and effective. The triazine-activated silica is relatively stable and can be installed for at least 1 month without obvious loss of reactivity when stored below 30 degrees C, pH below 7. It was observed that the amount of bound HSA reached 120 mg/g silica calculated from the UV absorbance difference of the HSA solution. d, l-tryptophan was selected as the probe solute to characterize the properties of HSA bonded s-triazine chiral stationary phase, and separation factor of 9.4 was obtained for d,l-tryptophan. Furthermore, the amount of effective HSA on silica was measured by high-performance frontal analysis, and only 16.8 mg/g silica was responsible for the resolution of d,l-tryptophan. These results indicate that the amount of both the bound and effective HSA on silica with triazine as activator was much higher than those by the Schiff base coupling method. Different kinds of enantiomers were resolved successfully on the aminopropylsilica-bonded HSA s-triazine chiral stationary phase.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Optical resolution of alpha-alkyl phenyl acetonitriles by HPLC on cellulose triacetate chiral stationary phases coated on underivatized silica gel

Microcrystalline celluloses from two sources were used to prepare cellulose triacetate chiral stationary phases (CSPs) coated on underivatized silica gel, which shows discriminating chiral recognition for enantiomers. The chiral separation of four alpha-alkyl phenyl acetonitriles was investigated on the prepared CSPs. It was observed that the concentration of the coating solvent of phenol in dichloromethane plays an important role in the resolution of the solutes. A series of primary alcohols, including secondary and tertiary alcohols, were used as mobile phase modifiers to investigate the effect of the structures of these modifiers on the capacity factors (k') and the separation factors (alpha). Also, the effect of the concentration of alcohol on the capacity factors and separation factors was examined. The chiral recognition mechanism of alpha-alkyl phenyl acetonitriles on the prepared CSPs is discussed. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗
PubMed2000

An optical system for wireless detuning of parallel resonant circuits.

A new optical method of detuning parallel resonant circuits is described. This method involves the integration of a photoresistor in parallel with the inductor and capacitor of a parallel resonant circuit, in this case a magnetic resonance imaging (MRI) receiver coil. A fiberoptic cable extending the length of the interventional device is used in conjunction with an external light source to deliver light to the photoresistor. Exposing the photoresistor to light changes its bulk resistance and greatly lowers the Q of the parallel resonant circuit, effectively detuning it. By combining this optical detuning scheme with inductive coupling of the interventional device-mounted microcoils to a standard MRI coil, a completely wireless device for active device tracking has been created. This new device improves on current technology by simplifying device complexity and reducing patient risk by eliminating the need for electrical connections between the device-mounted microcoils to the MR receiver channel.

Equipment Design↗
PubMed2000

Active MR guidance of interventional devices with target-navigation.

This project incorporated a novel inductive coupling structure of three micro coils into an invasive device tip to determine both its tip position and orientation. Moreover, with the introduction of a new target-navigation technique the MR scan plane was defined automatically by the invasive device orientation and target tissue location. A time domain multiplexing technique was applied for simultaneous MR imaging and device tracking. Using these techniques, the acquired MR images always showed both the invasive device and its target tissue. Thus, roadmap images and their potential misregistration errors were avoided. A graphical user interface (GUI) was also designed to assist interventional physicians in monitoring and guiding the insertion of the interventional device. Ex vivo phantom and in vivo animal experiments were performed to test this new technique. The methods developed in this project provide a new active technique for interventional device guidance using MRI. Magn Reson Med 44:56-65, 2000.

Animals↗
PubMed2000

5'-UTR structural organization, transcript expression, and mutational analysis of the human Rab geranylgeranyl transferase alpha-subunit (RABGGTA) gene.

Hermansky-Pudlak syndrome (HPS) is a recessively inherited disease with dysfunction of several related subcellular organelles including platelet-dense granules, melanosomes, and lysosomes. Our recent identification of the mutation in murine Rab geranylgeranyl transferase alpha-subunit gene (Rabggta) in one mouse model of HPS, the gunmetal mouse, suggested that human patients with similar phenotypes might have mutations in the human orthologous RABGGTA gene. This prompted reanalysis of the 5'-untranslated structure of the human RABGGTA gene in normal individuals and in patients with deficiencies of platelet-dense granules (alphadelta-SPD), alpha granules (alpha-SPD or gray platelet syndrome, GPS) or alpha plus dense granules (alphadelta-SPD). We report the complete sequence of intron alpha of RABGGTA and demonstrate that exon alpha is immediately upstream of intron alpha. The exon/intron structural organization of the 5'-untranslated region (UTR) of human RABGGTA was found to be similar to that of the mouse Rabggta gene. However, exons alpha and introns alpha are not homologous between mouse and human. Features of the 5'-UTR of RABGGTA suggest it is a housekeeping gene. While obvious disease-causing mutations of human RABGGTA were not found in our existing SPD patients by sequencing its entire coding region, several polymorphisms of RABGGTA including a putative cryptic splicing mutation in intron 4 were identified. Knowledge of the 5'-UTR structure of RABGGTA and its common polymorphisms will be useful for mutation screening or linkage analysis in patients with albinism, thrombocytopenia, or platelet SPD.

5' Untranslated Regions↗
PubMed2000

Change of coagulation factor VIII and antithrombin III activity in bank-stored blood.

Coagulation factor VIII and antithrombin III activity were detected in 15 health donors. It was found that antithrombin III activity decreased obviously 12 h after blood drawing. It lost 56% of the activity at the 3rd day, and 70% of the activity at the 7th day. FVIII:c showed no obvious change after 24 h, until the 3rd day. It lost 40%-60% of the activity after 36 h and was reduced to the 30% of the original activity at the 5th day. Our results suggested that at the 3rd day coagulation factor VIII of bank-stored blood can be used to replenish antithrombin III, while bank-stored blood in one day can be used to replenish F VIII.

Adolescent↗
PubMed2000

Clinical application of surface mode on three-dimensional ultrasonography: a preliminary study.

To investigate the methology and evaluate the clinical value of surface mode on three-dimensional ultrasonography (3DUS) in static anatomical structures, 62 patients with various diseases were studied. The equipment used here was Voluson 530D 3DUS imaging system and 3D volume transducer with frequency being 3.0-5.0 MHz. The 3DUS rendering method was surface mode. The results showed that: 1) Surface mode of 3DUS could demonstrate clearly the anatomical characteristics of the region-of-interest (ROI) and the inner wall of lesions or organs that contained fluid. The anatomic details, such as location, size, shape, and number of the ROI, could be visualized intuitively; 2) The outer anatomic features (e.g. contour, edge, configuration, etc.) of some organs or lesions surrounded by fluid could be displayed clearly. It could be concluded that surface mode on 3DUS could provide more diagnostic information than two-dimensional ultrasonography (2DUS) in some cases and could served as a beneficial supplement to 2DUS in clinical practice.

Adolescent↗
PubMed2000

The effects of limb elevation and increased intramuscular pressure on nerve and muscle function in the human leg.

In this study we investigated the effects of increased intramuscular pressure (IMP) on nerve and muscle function in the leg and foot. In study A, muscle pressure was increased by inducing venous stasis in both legs, placed in plaster casts, of eight healthy subjects having a mean age of 29 years. The results from elevated and non-elevated limbs were compared. In study B, two different models for increasing IMP were studied in nine healthy subjects having a mean age of 32 years. The results of increased IMP and decreased blood perfusion pressure on local (= leg) and distal (= foot) function of muscle and nerve induced by venous stasis of a leg in a plaster cast and by external compression of the contralateral leg were compared. Contraction pressure of the tibialis anterior muscle in the leg was recorded. A biphasic compound muscle action potential was measured from the extensor hallucis brevis and the extensor digitorum muscles as an indication of foot muscle function. Muscle contraction pressure was 87 (SD 38) mm Hg in the vein-obstructed leg and 133 (SD 42) mm Hg in the externally compressed leg (P<0.05). In both studies the skin sensibility of the feet was significantly lower in the vein-obstructed elevated leg after 30 min (P<0.05). Vein stasis in an elevated human leg in a plaster cast defines a model for simulating imminent acute compartment syndrome with reversible neuromuscular dysfunction.

Action Potentials↗
PubMed2000

Mapping of centromeric regions on the molecular linkage map of rice (Oryza sativa L.) using centromere-associated sequences.

Genetic mapping of centromeres has been a challenge for plant geneticists. The objective of this study was to develop a new strategy for determining the locations of centromeric regions on genetic maps by mapping centromere-associated sequences, to make it possible to define the centromeric region of each chromosome as a single Mendelian locus on the molecular linkage map. Two DNA probes containing sequences specifically associated with the centromeres of grass species were used for genetic mapping. The centromere-associated sequences for all 12 rice chromosomes were mapped on the molecular map with either or both of the probes, and flanking molecular markers on one or both sides were localized 0 to 8 cM away. The map locations of the centromere-associated markers corresponded very well with the positions of centromeric regions determined previously using trisomic analyses for 11 of the 12 chromosomes. The precise mapping of the centromeric regions using these probes makes the molecular map a more complete and informative tool for genomic studies, which will facilitate studies of the structure and function of the rice centromeres. The simplicity of this technique, together with the fact that these probes are also associated with the centromeric regions in other grass species, may provide a general approach to the mapping of centromeric regions in the genomes of other cereal crops.

Base Sequence↗
PubMed2000

Lack of phosphotyrosine phosphatase SHP-1 expression in malignant T-cell lymphoma cells results from methylation of the SHP-1 promoter.

SHP-1 is an important negative regulator of signaling by several receptors including receptors for interleukin-2 (IL-2R) and other cytokines. SHP-1 acts by dephosphorylating the receptors and receptor-associated kinases such as IL-2R-associated Jak3 kinase. We found that SHP-1 protein was not detectable or greatly diminished in most (six of seven) T cell lines derived from various types of T cell lymphomas and all (eight of eight) cutaneous T-cell lymphoma tissues with a transformed, large-cell morphology. All T-cell lymphoma lines tested (eight of eight) expressed diminished amounts or no detectable SHP-1 mRNA. These T cell lines did not, however, carry any mutations in the SHP-1 gene-coding, splice-junction, and promoter regions. Importantly, SHP-1 DNA promoter region in the T cell lines was resistant to digestion with three different methylation-sensitive restriction enzymes. This resistance was reversed by treatment of the cells with a demethylating agent, 5-deoxyazacytidine. The treatment resulted also in the expression of SHP-1 mRNA and, less frequently, SHP-1 protein. The expression of SHP-1 protein was associated with dephosphorylation of the Jak3 kinase. These results show that lack of SHP-1 expression is frequent in malignant T cells and results from methylation of the SHP-1 gene promoter. Furthermore, they indicate that SHP-1 loss may play a role in the pathogenesis of T cell lymphomas by permitting persistence of signals generated by IL-2R and, possibly, other receptor complexes.

Azacitidine↗
PubMed2000

On-line characterization of the activity and reaction kinetics of immobilized enzyme by high-performance frontal analysis.

A microreactor by immobilized trypsin on the activated glycidyl methacrylate-modified cellulose membrane packed column was constructed. Immobilized trypsin mirrored the properties of the free enzyme and showed high stability. A novel method to characterize the activity and reaction kinetics of the immobilized enzyme has been developed based on the frontal analysis of enzymatic reaction products, which was performed by the on-line monitoring of the absorption at 410 nm of p-nitroaniline from the hydrolysis of N-alpha-benzoyl-DL-arginine-p-nitroanilide (BAPNA). The hydrolytic activity of the immobilized enzyme was 55.6% of free trypsin. The apparent Michaelis-Menten kinetics constant (Km) and Vmax values measured by the frontal analysis method were, respectively, 0.12 mM and 0.079 mM min(-1) mg enzyme(-1). The former is very close to that observed by the static and off-line detection methods, but the latter is about 15% higher than that of the static method. Inhibition of the immobilized trypsin by addition of benzamidine into substrate solution has been studied by the frontal analysis method. The apparent Michaelis-Menten constant of BAPNA (Km), the inhibition constant of benzamidine (Ki) and Vmax were determined. It was indicated that the interaction of BAPNA and benzamidine with trypsin is competitive, the Km value was affected but the Vmax was unaffected by the benzamidine concentration.

Enzymes, Immobilized↗
PubMed2000

A new method of predicting of gas chromatographic retention indices for polychlorinated dibenzofurans (PCDFs).

A new method has been developed to describe the quantitative relationship between molecular structures of PCDFs and their gas chromatographic retention indices on a 30-m fused silica column coated with DB-5 stationary phase. The regression equation is derived with a multiple correlation coefficient greater than 0.9995. The highest residual is 20 index units. The standard deviation is less than 7 index units. Using this regression equation, the retention indices of PCDFs for which data is not available have also been predicted.

Benzofurans↗
PubMed2000

Haptoglobin is a natural regulator of Langerhans cell function in the skin.

Langerhans cells (LC), the best-understood antigen presenting cells (APC) of the skin, are functionally plastic. Freshly obtained LC readily activate allogeneic T cells, but are incapable of activating autologous, naive T cells. When placed in culture in the presence of GM-CSF, LC up-regulate surface expression of class I and II MHC molecules along with co-stimulatory molecules, such as B7, CD40 and IL-12. This functional transformation enables the cells to activate naive, autologous T cells in vitro. It is paradoxical that intracutaneous administration of exogenous GM-CSF fails to induce intraepidermal LC to undergo functional transformation in situ. It has been reported that serum contains a factor that prevents fresh LC from undergoing functional transformation in culture, and the relevant serum factor has now been identified as haptoglobin (Hp), based on the following experimental results: (a) SDS-PAGE, amino acid sequencing, and mass spectrometric analyses of the inhibitory factor purified by high performance liquid chromatography (HPLC) from normal human serum revealed molecules completely homologous to Hp alpha-1 chain; (b) pure human Hp, but not serum depleted of Hp, inhibited fresh LC from acquiring the capacity to activate autologous T cells in vitro; (c) abundant Hp was detected in cytoplasmic compartments of fresh, but not cultured, LC. It was concluded that Hp, an acute phase protein, is a systemically-derived factor that prevents epidermal LC from spontaneously undergoing functional maturation in the skin. This novel property of Hp may be important in ameliorating or preventing certain T cell-dependent inflammatory skin diseases.

Animals↗
PubMed2000

semang affects the development of a subset of cells in the Drosophila compound eye.

semang (sag), a mutation isolated as a suppressor of Drosophila Src42A, has previously been shown to affect some receptor tyrosine kinase mediated embryonic processes. Here we show that sag specifically affects the development of R1, R6 and R7 photoreceptor cells in a cell-autonomous manner. These cells are absent in the mutant at the time when they normally appear in the ommatidial pre-clusters. Genetic analyses suggest that sag functions downstream of, or parallel to, Mapk and Yan in the photoreceptor differentiation pathway. The autonomous requirement of sag for R1/R6/R7 development could be explained by a selective impairment of the late, but not early, rounds of Egfr-induced precursor cell assembly by the sag mutations. Egfr signaling is highly regulated by autocrine or paracrine mechanisms in different cells. Knowing that the photoreceptor cluster formation is a complex process involving dynamic changes in cell-cell contact, our hypothesis is that the sag alleles affected certain special aspects of Egfr-signaling that are unique for the recruitment of R1/R6/R7 cells.

Animals↗
PubMed2000

Diagnosis of diabetes by image detection of breath using gas-sensitive LAPS.

Gaseous respiratory acetone detection using LAPS (Light Addressable Potentiometric Sensors) is proposed as a supplementary method for the diagnosis of diabetes. First, electric simulation of the LAPS system is studied to obtain the optimum sensitivity of tested odours. Gas phase chromatography is used to obtain correlations between blood sugar levels and acetone from the breath. Then several experiments are carried out to obtain the 2-dimension static and dynamic images of respiratory acetone and air. All experimental results show that the LAPS can be very useful for the detection of respiratory odours, especially the diagnosis of diabetes.

Acetone↗
PubMed2000

Cernuosides A and B, two sucrase inhibitors from Pulsatilla cernua.

Two oleanane-type oligoglycosides, cernuosides A (1) and B (2), were isolated from the roots of Pulsatilla cernua (Ranunculaceae). Structure elucidation was accomplished by 1D and 2D NMR (DQF-COSY, TOCSY, HMQC, HMBC, and ROESY) methods, FABMS, and hydrolysis. Both compounds showed moderate activity against sucrase.

Animals↗
PubMed2000

Enoxaparin, a low molecular weight heparin, inhibits platelet-dependent prothrombinase assembly and activity by factor-Xa neutralization.

BACKGROUND: The available evidence suggests strongly that intravascular thrombosis is mediated predominantly by tissue-factor and its activation of factor X, which in the presence of factor Va, calcium, and phospholipid (prothrombinase complex) effectively converts prothrombin to thrombin. In vitro experiments have shown that low molecular weight heparins (LMWHs) have greater anti-Xa activity than unfractionated heparin; however, it remains unclear as to whether their antithrombotic effects in vivo are determined by a similar mechanism. We determined the ability of plasma obtained from patients with either unstable angina or non-ST segment elevation myocardial infarction (MI) receiving the LMWH enoxaparin (anti Xa:IIa ratio 3:1) to inhibit tissue factor-mediated thrombin generation and to inactivate platelet prothrombinase. METHODS: Platelet rich plasma was prepared by suspending washed donor platelets in the plasma of 7 patients participating in the TIMI 11A study. Samples were obtained before, 1 hour after a 30-mg IV bolus of enoxaparin and 6 hours after the third subcutaneous injection (1. 0-1.25 mg/kg given subcutaneously every 12 hrs). Tissue factor (0.1 ng/ml) and 10 mM CaCl(2) were added to initiate extrinsic coagulation. At timed intervals prothrombin activation fragment 1.2 (F1.2) levels (thrombin generation) were measured using an ELISA technique. Inactivation of reformed platelet prothrombinase by samples obtained at the same time points was also determined. RESULTS: Patient plasma obtained 1 hr after treatment initiation and 6 hours after the third subcutaneous injection inhibited tissue factor mediated prothrombinase assembly by 31% and 11%, respectively and platelet prothrombinase activity by 27% and 22%, respectively. CONCLUSION: We conclude that enoxaparin in plasma concentrations achieved routinely in clinical practice is able to: (1) inhibit tissue factor mediated extrinsic coagulation by preventing platelet surface prothrombinase assembly, and (2) inactivate platelet prothrombinase activity and resulting thrombin generation. These observations suggest that a LMWH's anti-Xa activity (and anti-Xa:IIa profile) is important in determining its overall antithrombotic potential. Clinical trials comparing agents with differing anti-Xa:IIa properties will be required, however, to provide proof of concept.

Angina, Unstable↗