Biomedical subjects

Y Jia

Publications and source records attributed to Y Jia.

At least 37 records · Page 2Linked to original sources

PubMed2001

Effects of random potential on transport.

The effects of random potential on the transport of two systems, which are the motion of motor proteins along a biopolymer and the thermally assisted vortex diffusion in layered high-Tc superconductors, are investigated, respectively. It is found that the effects of the random potential on the transport process as the amplitude of random potential increased are much more remarkable than those as the correlation length of random potential increased. The amplitude and the correlation length of random potential play opposing roles in the transport of the systems.

Biophysical Phenomena↗

PubMed2001

Effects of colored noise on stochastic resonance in a bistable system subject to multiplicative and additive noise.

The effects of colored noise on stochastic resonance (SR) in a bistable system driven by multiplicative colored noise and additive white noise and a periodic signal are studied by using the unified colored noise approximation and the theory of signal-to-noise ratio (SNR) in the adiabatic limit. In the case of no correlations between noises, there is an optimal noise intensities ratio R at which SNR is a maximum that identifies the characteristics of the SR when the correlation time tau of the multiplicative colored noise is small. However, when tau is increased, a second optimal value of R appears, and two peaks appear in the SNR simultaneously. In the case of correlations between noises, the SNR is not only dependent on the correlation time tau, but also on the intensity of correlations between noises. Moreover, the double peak phenomenon can also appear as tau is increased in certain situations.

Journal Article↗

PubMed2001

Mechanistic studies on class I polyhydroxybutyrate (PHB) synthase from Ralstonia eutropha: class I and III synthases share a similar catalytic mechanism.

The Class I and III polyhydroxybutyrate (PHB) synthases from Ralstonia eutropha and Chromatium vinosum, respectively, catalyze the polymerization of beta-hydroxybutyryl-coenzyme A (HBCoA) to generate PHB. These synthases have different molecular weights, subunit composition, and kinetic properties. Recent studies with the C. vinosum synthase suggested that it is structurally homologous to bacterial lipases and allowed identification of active site residues important for catalysis [Jia, Y., Kappock, T. J., Frick, T., Sinskey, A. J., and Stubbe, J. (2000) Biochemistry 39, 3927-3936]. Sequence alignments between the Class I and III synthases revealed similar residues in the R. eutropha synthase. Site-directed mutants of these residues were prepared and examined using HBCoA and a terminally saturated trimer of HBCoA (sT-CoA) as probes. These studies reveal that the R. eutropha synthase possesses an essential catalytic dyad (C319-H508) in which the C319 is involved in covalent catalysis. A conserved Asp, D480, was shown not to be required for acylation of C319 by sT-CoA and is proposed to function as a general base catalyst to activate the hydroxyl of HBCoA for ester formation. Studies of the [(3)H]sT-CoA with wild-type and mutant synthases reveal that 0.5 equiv of radiolabel is covalently bound per monomer of synthase, suggesting that a dimeric form of the enzyme is involved in elongation. These studies, in conjunction with search algorithms for secondary structure, suggest that the Class I and III synthases are mechanistically similar and structurally homologous, despite their physical and kinetic differences.

Acyl Coenzyme A↗

PubMed2001

Immunosuppressive sesquiterpene alkaloids from Tripterygium wilfordii.

Nine new sesquiterpene pyridine alkaloids [wilfornines A (1), B (2), C (3), D (4), E (5), F (8), and G (9); wilfordinines I (6) and J (7)] and six known compounds (10-15) were isolated from a clinically used extract (T(II)) of Tripterygium wilfordii. The structures of 1-9 were elucidated by spectroscopic and chemical methods. The inhibitory effects on cytokine production of 1-3 and several related compounds were evaluated. Compounds 10 and 14 showed significant inhibitory effects on cytokine production.

Alkaloids↗

PubMed2001

Crystal structure of the complex of concanavalin A and tripeptide.

The X-ray structure analysis of a cross-linked crystal of concanavalin A soaked with the tripeptide molecule as the probe molecule showed electron density corresponding to full occupation in the binding pocket. The site lies on the surface of concanavalin A and is surrounded by three symmetry-related molecules. The crystal structure of the tripeptide complex was refined at 2.4-A resolution to an R-factor of 17.5%, (Rfree factor of 23.7%), with an RMS deviation in bond distances of 0.01 A. The model includes all 237 residue of concanavalin A, 1 manganese ion, 1 calcium ion, 161 water molecules, 1 glutaraldehyde molecule, and 1 tripeptide molecule. This X-ray structure analysis also provides an approach to mapping the binding surface of crystalline protein with a probe molecule that is dissolved in a mixture of organic solvent with water or in neat organic solvent but is hardly dissolved in aqueous solution.

Binding Sites↗

PubMed2001

Crystal structure of the complex of concanavalin A and hexapeptide.

The X-ray structure analysis of a cross-linked crystal of concanavalin A soaked with a hexapeptide molecule as a probe molecule showed an electron density corresponding to full occupation in the binding pocket. The site lies on the surface of concanavalin A and is surrounded by three symmetry-related molecules. The crystal structure of the hexapeptide complex was refined at 1.93-A resolution, to an R-factor of 19% (Rfree factor of 25%), with an RMS deviation in bond distances of 0.01 A. The model includes all 237 residues of concanavalin A, one manganese ion, one calcium ion, 95 water molecules, one glutaraldehyde molecule, one isopropanol molecule, and one hexapeptide molecule. This X-ray structure analysis also provides an approach to mapping the binding surface of crystalline protein with a probe molecule that is dissolved in the mixture of organic solvent with water or in neat organic solvent but is hardly dissolved in aqueous solution.

Binding Sites↗

PubMed2001

Acquired esotropia: subjective and objective outcomes.

PURPOSE: The measurement of outcomes of pediatric therapy will be increasingly important to third-party payers as they allocate health care resources. We undertook this study to assess the effectiveness of treatment of acquired esotropia, as measured subjectively by parents and objectively by examination. METHODS: A chart review was used to gather objective clinical data from all patients presenting between 1994 and 1995 with esotropia after their first birthday. Parents' impressions of the quality and impact of treatment were tabulated by using a telephone questionnaire. RESULTS: Of 48 patients studied (mean age, 3.8 years; 44 months' follow-up), the 26 with amblyopia were effectively treated in 81% of cases. Mean esotropic angles decreased, with glasses and/or surgery, from 33.1 to 4.9 PD at distance and from 40.0 to 11.4 PD at near. The average estimated cost of care was 547 dollars per patient per year. Parents considered treatment "extremely important" to their child's future happiness and success in 90% of cases. CONCLUSION: Our experience has shown that treatment of acquired esotropia in childhood, while relatively inexpensive, is highly effective, both objectively and subjectively.

Child↗

PubMed2001

Effects of matrix proteins on the expression of matrix metalloproteinase-2, -9, and -14 and tissue inhibitors of metalloproteinases in human cytotrophoblast cells during the first trimester.

The activity of matrix metalloproteinases (MMPs) specifies the ability of the trophoblast cell to degrade extracellular matrix (ECM) substrates. Usually the process of normal human placentation involves a coordinated interaction between the fetal-derived trophoblast cells and their microenvironment in the uterus. In this study, the effects of ECM proteins on the expression of MMP-2, -9, and -14 (membrane-type MMP-1); and the production of tissue inhibitors of metalloproteinase (TIMP) types -1, -2, and -3 have been investigated. Cytotrophoblast cells at 9 or 10 wk of gestation were cultured on various ECM coated dishes under serum-free conditions. Gelatin zymography analysis showed that cells grown on fibronectin (FN), laminin (LN), and vitronectin (VN) secreted more MMP-9 (about 1.5- to 3-fold more) than cells cultured on collagen I (Col I), whereas the secretion of MMP-9 by cells cultured on collagen IV (Col IV) was only half that by the cells on Col I. Northern Blot analysis gave the same results as zymography, indicating that expression of the MMP-9 gene in cytotrophoblast cells can be affected by matrix proteins. There was no significant difference in the expression of MMP-2 either at protein or mRNA levels among the cells cultured on the different matrix substrates. The expression of MMP-14 was regulated in a manner similar to that of MMP-2. Using ELISA, we detected higher levels of TIMP-1 in the culture medium of cells grown on VN, LN, and FN compared with that grown on Col I. But the expression of TIMP-3 mRNA was remarkably inhibited by VN, and ECM proteins had no effect on TIMP-1 and TIMP-2 mRNA expression. It was also observed that cultured cytotrophoblast cells expressed the corresponding receptors for the tested matrix proteins, such as integrins alpha(1), alpha(5), alpha(6), beta(1), and beta(4). Furthermore, the adhesiveness of cytotrophoblast cells on Col I, Col IV, FN, and LN was increased by 62%, 45%, 21%, and 22%, respectively, when compared with adhesiveness on VN. Isolated cytotrophoblast cells remained stationary when cultured on dishes coated with Col I and Col IV, but they assumed a more motile morphology and aggregated into a network when cultured on LN and VN. These data indicate that human trophoblast cells interact with their microenvironment to control their behavior and function.

Adult↗

PubMed2001

Hepatitis B virus transgenic mice for the model of anti-hepatitis B virus drug study.

OBJECTIVE: To establish hepatitis B virus (HBV) transgenic mice models and to investigate if the model can be used for the evaluation of anti-HBV drugs. METHODS: HBV transgenic mice models were produced by microinjection to analyze the integration, expression of HBV in the transgenic mice by nested PCR, southern blot, immunohistochemistry, and ELISA. Sixty mice whose HBV DNA, HBsAg were positive were divided into 6 groups randomly, in which 3 groups were given drugs: lamivudine administrated by perfusion of stomach tube (100mg x kg(-1) x day(-1) for 21 days); thymosine administrated by abdomen injection (3mg x day(-1) for 90 days); and DNA vaccine of 100 microg by muscle injection. The other 3 groups were negative control. RESULTS: Lamivudine, thymosine and DNA vaccine made HBV DNA become negative in the serum of HBV transgenic mice. The negative ratio was highest in lamivudine treatment group. HBV DNA became positive again when lamivudine terminated. CONCLUSION: Limvudine, thymosine, and DNA vaccine can inhibit HBV replication. Transgenic mice might be used as the model for anti-HBV drug screening and evaluation.

Animals↗

PubMed2001

Treatment of nonspecific chronic prostatitis with Qian Lie Xian Yan Suppository suppository in 104 cases.

Qian Lie Xian Yan Suppository ([symbol: see text]) was rectally applied to treat 104 patients with nonspecific chronic prostatitis (damp-heat syndrome with blood stasis) in contrast to 30 patients treated with traditional Chinese drug Ye Ju Hua Shuan ([symbol: see text] Suppository of Flos Chrysanthemi Indici). The results show that chronic prostatitis is markedly improved by using Qian Lie Xian Yan suppository, with a short-term cure rate of 23.1% and a total effective rate of 84.6%, superior to that of the control group. The animal experiment indicates that Qian Lie Xian Yan suppository has better anti-inflammatory and analgesic effects, with an action of promoting blood circulation.

Administration, Rectal↗

PubMed2001

[Clinical study of preoperative orthodontic treatment for patients with cleft lip and palate].

OBJECTIVE: To discuss the indication and time of preoperative orthodontic treatment for the patients with cleft lip and palate. METHODS: 16 cleft lip and palate patients (BCLP 6, UCLP 10) with severe cross-bite were selected. Edgewise appliance was used for the alignment and upper arch was expanded with quadhelix. RESULTS: After the orthodontic treatment, upper and lower arches were well aligned and the arch form was normal. Decompensation was achieved. Model surgery revealed that the upper and lower arches were harmonious. CONCLUSION: Preoperative orthodontic treatment is the key point to ensure the success of the surgery and to prevent relapse. Orthodontic/surgical approach can improve the patients' profile and function.

Adolescent↗

PubMed2001

[Effects of aluminum on amino acid neurotransmitters in hippocampus of rats].

OBJECTIVES: To study the effects of long-term exposure to aluminum on amino acid transmitters in hippocampus of rats. METHODS: Sprague-Dawley rats were randomly divided into four groups based on their body weight. Aluminum chloride was added into diet at doses of 0, 11.2, 55.9 and 111.9 mg/kg BW for 90 days successively. Neurobehavioral testing consisted of open field and passive-avoidance conditioning. The contents of amino acids were detected by HPLC. Aluminum was measured by atomic absorption spectroscopy. RESULTS: The spontaneous motor ability in the open field and the latency of passive avoidance in aluminum treated rats were decreased as compared with the controls. In hippocampus, the contents of aspartate (Asp) and glutamine (Gln) were significantly increased at the dose of 111.9 mg Al3+/kg BW (P < 0.05, P < 0.01), while taurine (Tau) was significantly increased at doses of 55.9 and 111.9 mg Al3+/kg BW(P < 0.05) as compared with control. The increased values of aluminum were significantly related to the dosage of aluminum. CONCLUSION: The altered content of amino acid neurotransmitters in hippocampus might be one of the important mechanisms of aluminum neurotoxicity.

Aluminum↗

PubMed2001

One hundred and seven middle-aged and senile cases of coronary heart disease with ventricular premature beat treated by qing xin an shen fang.

The therapeutic principle of clearing away the heart-heat to induce tranquilization was adopted in 107 middle-aged and senile patients with ventricular premature beat of coronary heart disease on the basis of pathogenic features of phlegm, heat, blood stasis and deficiency in this condition. Qing Xin An Shen Fang ([symbol: see text] a formula for clearing away the heart-heat to induce tranquilization) was used in the treatment group and compared with mexiletine and Fu Fang Dan Shen Tablets ([symbol: see text] Compound Salvia Tablets) used in the control group. The results turned to be that the markedly effective rate was 85.1% and the total effective rate 96.3% in the treated group, better than that in the control group, with the former having a good antihypertensive and antihyperlipemic effect and an effect of improving microcirculation and clinical symptoms.

Aged↗

PubMed2001

[Effects of aluminum intake on the content of aluminum, iron, zinc and lipid peroxidation in the hippocampus of rats].

Effect of long-term exposure to aluminum on the content of aluminum, iron, zinc, copper and the lipid peroxidation in hippocampus was studied. Sprague-Dawley rats were randomly divided into four groups by body weight. Aluminum chloride was added to diet at doses of Al3+ 0, 11.2, 55.9 and 111.9 mg/kg BW for successive 90 days. Neuro-behavioral tests consisted of open field and passive-avoidance conditioning were performed. SOD and GSH-Px activities and MDA levels were detected by spectrophotometry. The values of aluminum, iron, zinc and copper were measured by atomic absorption spectroscopy. The spontaneous motor ability in the open field and the latency of passive avoidance were decreased as compared with the controls. The concentration of aluminum was increased and iron and zinc were decreased copper was not changed significantly; the activities of SOD and GSH-Px were reduced, while the value of MDA was increased in hippocampus. The results suggested that long-term aluminum-exposure could lead to high accumulation of aluminum in hippocampus, which could disturb the normal distribution of iron and zinc, decrease the activities of antioxidase and increase the level of lipid peroxidation. Accumulation of aluminum and accompany with reduction of iron, zinc in hippocampus and oxidative damage to hippocampus might interpret the neurotoxicity of aluminum.

Aluminum↗

PubMed2001

[Study on interaction between the metal ion in the active site of cytochrome C and trace elements by ultraviolet spectroscopy].

The direct interaction between the metal ion in the active center of cytochrome C(Fecyt-C) and four trace elements in pH 7.1 phosphate buffer by UV spectrometry has been studied. As a result, part of the metal ion Fe(II) in Fecyt-C was replaced and the corresponding cytochrome C derivatives were produced. The Soret absorption maximum is blue-shifted and the absorption coefficient of the alpha band relative to that of the beta band is decreased in comparison to the Fecyt-C.

Copper↗

PubMed2001

[Determination of potassium in sodium by flame atomic emission spectroscopy].

Sodium is used as a coolant in China experiment fast reactor (CEFR). Potassium in sodium has an influence on heat property of reactor. A analytical method has been developed to determinate potassium in sodium by flame atomic emission spectroscopy. Sodium sample is dissolved by ultrasonic humidifier. The working conditions of the instrument and inTerferences from matrix sodium, acid effect and concomitant elements have been studied. Standard addition experiments are carried out with potassium chloride. The percentage recoveries are 94.7%-109.8%. The relative standard deviation is 4.2%. The analytical range accords with sodium quality control standard of CFFR. The precision corresponds to the international analytical method in sodium coolant reactor.

Potassium↗

PubMed2001

[Interaction between the metal ion in the active site of cytochrome C and copper sulfate by ultraviolet spectroscopy].

The direct interaction between the metal ion in the active center of cytochrome C (Fecyt-C) and inorganic copper sulfate in pH 7.1 phosphate has been studied by UV spectrometry. As a result, part of the metal ion Fe(II) in Fecyt-C was replaced by Cu(II) and the corresponding cytochrome C derivatives Cucyt-C were produced, in addition, the interaction was increased with amount of copper sulfate added. The direct interaction between the CuSO4 and metal ion of cytochrome C was verified for the first time.

Cations↗

PubMed2000

Dynamics and folding of single two-stranded coiled-coil peptides studied by fluorescent energy transfer confocal microscopy.

We report single-molecule measurements on the folding and unfolding conformational equilibrium distributions and dynamics of a disulfide crosslinked version of the two-stranded coiled coil from GCN4. The peptide has a fluorescent donor and acceptor at the N termini of its two chains and a Cys disulfide near its C terminus. Thus, folding brings the two N termini of the two chains close together, resulting in an enhancement of fluorescent resonant energy transfer. End-to-end distance distributions have thus been characterized under conditions where the peptide is nearly fully folded (0 M urea), unfolded (7.4 M urea), and in dynamic exchange between folded and unfolded states (3.0 M urea). The distributions have been compared for the peptide freely diffusing in solution and deposited onto aminopropyl silanized glass. As the urea concentration is increased, the mean end-to-end distance shifts to longer distances both in free solution and on the modified surface. The widths of these distributions indicate that the molecules are undergoing millisecond conformational fluctuations. Under all three conditions, these fluctuations gave nonexponential correlations on 1- to 100-ms time scale. A component of the correlation decay that was sensitive to the concentration of urea corresponded to that measured by bulk relaxation kinetics. The trajectories provided effective intramolecular diffusion coefficients as a function of the end-to-end distances for the folded and unfolded states. Single-molecule folding studies provide information concerning the distributions of conformational states in the folded, unfolded, and dynamically interconverting states.

Amino Acid Sequence↗