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Biomedical subjects

L Tao

Publications and source records attributed to L Tao.

At least 91 records · Page 5Linked to original sources
PubMed1999

Detection and nucleotide analysis of RNA5 of beet necrotic yellow vein virus isolated in China.

Using the RT-PCR method, five isolates of beet necrotic yellow vein virus from China were used for the RNA5 genomic component detection and sequence analysis. The result showed that RNA5 was only found in the isolates from Baotou and Hohhot, but not in those of Xingjiang, Helongjiang, and Wulate of Inner Mongolia. The RNA5 components had 1338 nucleotides and 1358 nucleotides in the length of Baotou and Hohhot isolates, respectively, in which the single open reading frame (ORF) encoding for a proteins of 26kD were contained. Compared with the published sequences of F72 and D5 isolates, these RNA5 components shared the identity of 93.7% approximately 98.5% in nucleotide acids and 91.8%-98.2% in deduced amino acids.

Base Sequence↗
PubMed1999

[Three dimensional finite element analysis of effects on composite resin for filling in various cavity margin design].

OBJECTIVE: To evaluate the stress distribution of different angles of cavity margins with composite resin filling. METHODS: The stress distributions of different angles of cavity margins of class I cavity of molars were analyzed by the method of three dimensional finite element. The cavity was filled with composite resin and the stress vertical force and lateral force was calculated. RESULTS: In the 5 designed different cavity margin angles, the vertical forces and lateral forces were 18.757 MPa and 22.309 MPa respectively when the angle is 90 degrees; when the angles were 75 degrees and 60 degrees, they were 10.580 MPa, 14.265 MPa and 9.025 MPa, 13.230 MPa respectively. The vertical forces and lateral forces produced by the surface of composite resin while being stressed were up to 18.757 MPa and 22.309 MPa. The forces of the second layer evidently reduced to 2.586 MPa and 6.8 MPa. CONCLUSION: When fill the molars with resin in clinic, the angles of cavity margins should be prepared with the slopes of 60 degrees to 75 degrees.

Composite Resins↗
PubMed1999

[Investigation of the bone mineral density in hemodialysis patients for different terms].

The investigate the change of bone mineral density(BMD) in hemodialysis patients for different terms of hemodialysis, 50 patients were divided into three groups according to the duration of hemodialysis. Group I was < 5 years. Group II was 5-10 years, and Group III > 10 years. The BMD of the patients were assayed by using dual energy X-ray bone absorptiometer. Serum calcium, phosphorus, aluminium, and intact parathyroid hormone(iPTH) were detected at the same time. The mean BMD and serum iPTH were 0.624 +/- 0.180 g.cm-2 and 9.67 +/- 9.46 ng.cm-1 in Group I, 0.573 +/- 0.160 g.ml-2 and 10.16 +/- 28.05 ng.ml-1 in Group II, and 0.513 +/- 0.117 g.cm-2 and 10.75 +/- 24.94 ng.ml-1 in Group III, respectively. There was no statistical significance in BMD (P > 0.05) and iPTH(P > 0.05) among the above groups. The BMD of hemodialysis patients is not affected by different terms of hemodialysis.

Bone Density↗
PubMed1999

[Studies on chemical constituents of Forsythia suspensa (Thunb) Vahl].

OBJECTIVE: To study the chemical constituents of Forsythia suspensa. METHOD: Basedon silicacolumn chromatography, of which six compounds were obtained from the alcohol extract of F. suspensa, three identified by physicochemical and spectroscopic analyses. RESULT: The three compounds were identified as stearic acid, palmitic acid and beta-sitosterol. CONCLUSION: The three compounds were separated from F. suspensa fruits for the first time.

Forsythia↗
PubMed1999

[Effection of children airway foreign bodies on blood acid-base disturbances].

OBJECTIVE: To explore the effects of children airway foreign bodies on blood acid-base disturbances. METHOD: To detect the blood-gas and electrolyte of 50 cases by children airway foreign bodies (test group), they were compared with 50 cases normal children (control group). To calculate anion gap (AG), to determine types of acidbase disturbances. RESULT: The blood-gas and K+ were significant difference between that two groups. In the test group, there were 25 simple and 19 mixed acid-base disturbances; 6 acid-base balances. There were 31 high AG, 18 normal AG, one low AG. CONCLUSION: Children airway foreign bodies can cause acid-base disturbances. It was major in simple metabolic acidosis and mixed metabolic acidosis with respiratory alkalosis, it was more in high AG-metabobic acidosis.

Acid-Base Imbalance↗
PubMed1999

[Correlation of conformational change with enzyme activity of glucose isomerase in denaturants monitored with high performance liquid chromatography].

Glucose isomerase (GI) can catalyze in vitro the isomerization of D-glucose to D-fructose. So it is an extremely important industrial enzyme in the commercial conversion of starch to high fructose syrups. In the previous papers, we have purified and characterized the enzyme from streptomyces diastaticus M1033 of China and obtained the crystal structures by X-ray. In this paper, a method for measurement of the dynamic conformational change procedure of glucose isomerase in various concentrations of denaturants by HPLC has been established. At first the relative molecular mass of GI in solution is measured by HPLC on PROTEIN PAK 300SW (7.5 mm i.d. x 30 cm) column. The relative molecular mass of GI is about 150,000. So GI exists as tetramer in the solution without denaturants. In 0-5 mol/L guanidine hydrochloride, incubated at 30 degrees C for 30 min, GI is gradually dissociated into monomer, and at the same time its activity gradually disappears. In various concentrations of urea and incubation at 30 degrees C for 30 min (or 60 degrees C for 1 h), the results are different from that in guanidine, because the monomers peaks of GI is not found. Only in certain concentrations of urea, the small dimer peaks of GI is found, but the activity of GI significantly disappears. Moreover as the increase of the urea concentration, the retention time of tetramer peak is gradually decreases. From the fluorescence spectra, we found the conformation of GI changed in the solution of urea. So perhaps in urea, the conformation of GI become a little unfolded, and the active region is partly damaged, which makes GI partly inactive. Dissociation into inactive monomers and conformation partly unfolding are all the reason of GI inactivation in denaturants.

Aldose-Ketose Isomerases↗
PubMed1999

A study on PCR for detecting infection with M. leprae.

OBJECTIVE: So far, it has not been established a satisfactory method for early diagnosis and studying on epidemiology for leprosy, we want to develop a molecular biological method for solving this point. MATERIALS AND METHODS: Based on the M. leprae gene coding groEL, 65 kD and 16S rRNA, three polymerase chain reactions were developed by using Plikaytis', Woods' and Pattyn's procedures. It was optimized that the experimental parameters for each PCR, and a comparative study on practivity among three PCRs was also conducted for practical purpose. RESULTS AND CONCLUSION: For detecting infection with M. leprae, all of PCRs established by us were highly sensitive and specific, but for practical purpose, the Woods' PCR optimized by us ought to be chosen firstly.

Chaperonin 60↗
PubMed1998

Stellar oscillons.

We study the weakly nonlinear evolution of acoustic instability of a plane-parallel polytrope with thermal dissipation in the form of Newton's law of cooling. The most unstable horizontal wavenumbers form a band around zero and this permits the development of a nonlinear pattern theory leading to a complex Ginzburg-Landau equation (CGLE). Numerical solutions for a subcritical, quintic CGLE produce vertically oscillating, localized structures that resemble the oscillons observed in recent experiments of vibrated granular material.

Journal Article↗
PubMed1998

Structure and developmental expression of the mouse RGR opsin gene.

PURPOSE: The aim of this study is to isolate and characterize cDNA clones and the genes that encode mouse RPE retinal G protein-coupled receptor (RGR) and to analyze expression of the RGR gene in the developing mouse retina. The conserved amino acid sequences of RGR from various mammals can be compared to the amino acid sequence motif of G protein-coupled receptors. METHODS: Mouse RGR cDNA and gene clones were isolated from a retina cDNA library and 129SV genomic DNA library, respectively. The expression of RGR in the developing C57BL/6J mouse retina was analyzed by immunohistochemical staining with a polyclonal antipeptide antibody. RESULTS: The deduced amino acid sequence of mouse RGR is 78% and 81% identical to that of bovine and human RGR, respectively. The mouse RGR gene is split into seven exons and extends about 11 kb. Two predominant mRNA transcripts, 1.9 and 1.7 kb in length, and a third, relatively faint, 5.5-kb transcript were detected in mouse eye by hybridization to a RGR cDNA probe. Frozen sections of C57BL/6J mouse retina at various stages of development were incubated with a mouse RGR antipeptide antibody. RGR immunoreactivity was first seen at postnatal day 2 (P2) in centrally located RPE cells. From day P6 to P12, there was an increase in the number and intensity of immunoreactive RPE cells in the central and mid-peripheral regions of the retina, while the most peripheral RPE cells were still negative. By day P16, the length of the RPE monolayer was immunoreactive, and staining of the central RPE cells was markedly more intense than at younger ages. CONCLUSIONS: Mouse and human RGR are highly conserved. A gradient of RGR expression in RPE extends from the central to the peripheral retina during development. In reference to the appearance of melanin-positive differentiated RPE cells, the induction of RGR expression is a relatively late event in the maturation of the retina.

Aging↗
PubMed1998

Solution structure of a fragment of the dimerization domain of E2F-1 determined by circular dichroism, 1H nuclear magnetic resonance and distance geometry.

The structure of a synthesized peptide with the sequence GVVDLNWAAEVLKVQKRRIYDITNVLEGIQ which corresponds to residues 149-178 of transcription factor E2F-1 was determined by 1H nuclear magnetic resonance in 40% d3-TFE/water. NOE cross peaks and alphaH chemical shifts indicate that the peptide consists of a helix from Ala-8 to Leu-26 in this solution. Circular dichroism measurements confirm the presence of nearly 45% helix in TFE/water solution but show no evidence of helicity in water solution of this peptide. Fifty structures were constructed with 329 upper distance limits by DIANA. The 20 best conformers show a RMSD of 0.78 A for backbone atoms and 1.78 A for heavy atoms from residue Ala-8 to Leu-26. This result, together with our previous work on the solution structure of a fragment of DP-1, supports the proposal that E2F-1 and DP-1 may dimerize with a coiled-coil type interaction.

Amino Acid Sequence↗
PubMed1998

Generation of CD8 suppressor factor and beta chemokines, induced by xenogeneic immunization, in the prevention of simian immunodeficiency virus infection in macaques.

Previous xenogeneic immunization experiments in rhesus macaques with simian immunodeficiency virus (SIV) grown in human CD4(+) T cells consistently elicited protection from challenge with live SIV. However, the mechanism of protection has not been established. We present evidence that xenogeneic immunization induced significant CD8 suppressor factor, RANTES (regulated upon activation, normal T cell expressed and secreted), macrophage inflammatory protein (MIP) 1alpha, and MIP-1beta (P < 0.001 - P < 0.02). The concentrations of these increased significantly in protected as compared with infected macaques (P < 0.001). Xenogeneic stimulation in vitro also up-regulated CD8 suppressor factors (SF; P < 0.001) and the beta chemokines which were neutralized by antibodies to the 3 beta chemokines. Recombinant human RANTES, MIP-1alpha and MIP-1beta which bind to simian CCR5, suppressed SIV replication in a dose-dependent manner, with RANTES being more effective than the other two chemokines. The results suggest that immunization with SIV grown in human CD4(+) T cells induces CD8-suppressor factor, RANTES, MIP-1alpha and MIP-1beta which may block CCR5 receptors and prevent the virus from binding and fusion to CD4(+) cells.

Animals↗
PubMed1998

Quantification of carvone, cineole, perillaldehyde, perillyl alcohol and sobrerol by isocratic high-performance liquid chromatography.

A simple and rapid isocratic HPLC assay is presented for the analysis and quantification of monoterpenes, i.e., carvone, cineole, perillaldehyde, perillyl alcohol and sobrerol in the diet of laboratory animals. The monoterpenes were extracted from the diet using 90% methanol in water. The analysis for the monoterpenes was performed by HPLC using a Whatman PartiSphere C18 column with UV detection. The mobile phase was isocratic methanol-water (72:28, v/v) for carvone, cineole, perillaldehyde and perillyl alcohol and methanol-water (65:35, v/v) for sobrerol. The method was simple with good repeatability (R.S.D. = 4.2-16.1%), reproducibility (R.S.D. = 3.7-19%), and accuracy (R.S.D. = 5.5-23.3%). The detection limit of the monoterpenes extracted from the diet was 2 micrograms/g for carvone, perillaldehyde and sobrerol, 20 micrograms/g for perillyl alcohol and 100 micrograms/g for cineole. Excellent resolution was achieved between the monoterpenes and the constituents of the diet. The method demonstrated applicability to monitoring the formulation of monoterpenes in the diet of laboratory animals.

Animal Feed↗
PubMed1998

On-line competitive immunoassay based on capillary electrophoresis applied to monitoring insulin secretion from single islets of Langerhans.

An automated on-line competitive immunoassay based on capillary electrophoresis (CE) was utilized to monitor secretion of insulin from single islets of Langerhans stimulated by glucose and tolbutamide. In the instrument, fluorescein isothiocyanate-labeled insulin (FITC-insulin), monoclonal anti-insulin and perifusate of single islets were mixed on-line while islets were exposed to different levels of glucose and tolbutamide. Insulin released from single islets competed with FITC-insulin for antibody binding sites. Therefore, the amounts of bound and free FITC-insulin were modulated by insulin released from islets. The bound and the free FITC-insulin were separated by CE every 3 s and the bound over free ratio (B/F) was measured. Insulin levels were obtained by comparing B/F with calibration curves obtained under the same conditions except that the islet perfusate was replaced with various concentrations of insulin. Patterns of insulin secretion stimulated by glucose and tolbutamide observed were comparable to what has been seen previously using radioimmunoassay or enzyme-linked immunoassay. This on-line competitive immunoassay system provided a fast and direct way to measure insulin release from single islets. The effects of temperature on antibody-antigen reaction rate and binding equilibrium were also studied.

Animals↗
PubMed1998

Effect of dichloroacetic acid and trichloroacetic acid on DNA methylation in liver and tumors of female B6C3F1 mice.

Dichloroacetic acid (DCA) and trichloroacetic acid (TCA) are found in drinking water and are metabolites of trichloroethylene. They are carcinogenic and promote liver tumors in B6C3F1 mice. Hypomethylation of DNA is a proposed nongenotoxic mechanism involved in carcinogenesis and tumor promotion. We determined the effect of DCA and TCA on the level of DNA methylation in mouse liver and tumors. Female B6C3F1 mice 15 days of age were administered 25 mg/kg N-methyl-N-nitrosourea and at 6 weeks started to receive 25 mmol/liter of either DCA or TCA in their drinking water until euthanized 44 weeks later. Other animals not administered MNU were euthanized after 11 days of exposure to either DCA or TCA. DNA was isolated from liver and tumors, and after hydrolysis 5-methylcytosine (5MeC) and the four bases were separated and quantitated by HPLC. In animals exposed to either DCA or TCA for 11 days but not 44 weeks, the level of 5MeC in DNA was decreased in the liver. 5MeC was also decreased in liver tumors from animals exposed to either chloroacetic acid. The level of 5MeC in TCA-promoted carcinomas appeared to be less than in adenomas. Termination of exposure to DCA, but not to TCA, resulted in an increase in the level of 5MeC in adenomas to the level found in noninvolved liver. Thus, hypomethylated DNA was found in DCA and TCA promoted liver tumors and the difference in the response of DNA methylation to termination of exposure appeared to support the hypothesis of different mechanisms for their carcinogenic activity.

5-Methylcytosine↗
PubMed1998

Effects of taurine on signal transduction steps induced during hypertrophy of rat heart myocytes.

Angiotensin II plays an important role in the development of cardiac hypertrophy. One factor thought to contribute to the trophic activity of angiotensin II in fibroblasts is the elevation in [Ca2+]i. Although this theory has received considerable support in cardiac fibroblasts, it is much more controversial in cardiac myocytes. Therefore, the aim of this report was to examine the effect of several Ca2+ modulators on protein synthesis in neonatal cardiac myocytes. We found that angiotensin II increased both [Ca2+]i and the rate of protein synthesis in isolated myocytes. Both effects were blocked by nifedipine, but only the angiotensin II-mediated increase in [Ca2+]i was inhibited by taurine in a dose-dependent manner. These data support the notion that Ca2+ plays only a permissive role in angiotensin II-mediated stimulation of protein synthesis. By contrast, the ability of taurine to attenuate the positive chronotropic effect, the prolongation of the action potential and the proarrhythmic activity of angiotensin II appear to be linked directly to changes in [Ca2+]i. We conclude that taurine reverses these actions of angiotensin II by altering Ca2+ flux across the cell membrane.

Angiotensin II↗
PubMed1998

Hepatic uptake of hippurate: a multiple-indicator dilution, perfused rat liver study.

The hepatic transport of hippuric acid (HA), a glycine-conjugated metabolite of benzoic acid that exhibits only modest plasma albumin binding (binding association constant of 2.1 x 10(3) M-1), was studied in the single-pass perfused rat liver (12 ml/min), using the multiple indicator dilution (MID) technique. The venous recovery of [3H]HA on portal venous injection of a MID dose containing a mixture of a set of noneliminated reference indicators and [3H]HA revealed a survival fraction of unity, corroborating the lack of disappearance of bulk HA from plasma. When the outflow recovery was fitted to the barrier-limited model of Goresky et al. (C.A. Goresky, G. G. Bach, and B. E. Nadeau. J. Clin. Invest. 52: 991-1009, 1973), the derived influx (P(in)S) and efflux (P(out)S) permeability-surface area products were found to be dependent on the concentration of HA (1-930 microM); P(in)S and P(out)S were approximately 3.5 times the plasma flow rate at low HA concentration, but decreased with increasing HA concentration. All values, however, greatly exceeded the expected contribution from passive diffusion, because the equilibrium distribution ratio of chloroform to buffer for HA was extremely low (0.0001 at pH 7.4). The tissue equilibrium partition coefficient (P(in)/P(out), or ratio of influx to efflux rate constants, k1/k-1) was less than unity and decreased with concentration. The optimized apparent Michaelis-Menten constant and maximal velocity were 182 +/- 60 microM and 12 +/- 4 nmol.s-1.g-1, respectively, for influx and 390 +/- 190 microM and 29 +/- 13 nmol.s-1.g-1, respectively, for efflux. In the presence of L-lactate (20 mM), however, P(in)S for the uptake of HA (174 +/- 3 microM) was reduced. Benzoic acid (10-873 microM) was also effective in reducing hepatic uptake of HA (5.3 +/- 0.9 microM). These interactions suggest that MCT2, the monocarboxylate transporter that mediates the hepatic uptake of lactate and other monocarboxylic acids, may be involved in HA transport.

Animals↗
PubMed1998

[Relationship between left cardiac function and oxygen transport of cor pulmonale during acute attack at high altitude].

OBJECTIVE: Relationship between left cardiac function and oxygen transport in the patients with cor pulmonale during acute attack at high altitude was studied to benefit prevention and treatment of cor pulmonale. METHOD: 20 cases were divided into 16 as a surviving group and 4 as a death group. CO was determined by Swan-Ganz catheter from internal carotid vein to pulmonary artery directly. RESULT: (1) CI in the patients decreased (2.9 +/- 0.4 L.min-1.m-2). mPAP (4.9 +/- 1.3 kPa) and PAWP (1.5 +/- 0.8 kPa) increased. LVSWI (35 +/- 11 g.cm-1.min-1) dropped. (2) above Indicies in surviving group improved after comprehensive treatment. CI and LVSWI increased. But LVSWI in death group continued to decline. mPAP and PAWP were not changed; (3) There was significant corelation between LVSVI and DO2(r = 0.4318, P < 0.05). CONCLUSION: LVSWI of cor pulmonale could affect DO2 level directly and closely relate to prognosis.

Aged↗