Biomedical subjects

X J Guo

Publications and source records attributed to X J Guo.

At least 19 recordsLinked to original sources

PubMed2006

SPARC, an upstream regulator of connective tissue growth factor in response to transforming growth factor beta stimulation.

OBJECTIVE: To differentiate the effects of inhibition of specific small interfering RNA (siRNA) of SPARC (secreted protein, acidic and rich in cysteine) and siRNA of connective tissue growth factor (CTGF) in cultured human fibroblasts, and to identify potential interrelationships between SPARC and CTGF. METHODS: Fibroblasts from skin biopsy specimens of 2 normal individuals were transfected with siRNA of SPARC and siRNA of CTGF. The fibroblasts were stimulated with or without transforming growth factor beta1 (TGFbeta1) and examined by real-time quantitative reverse transcription-polymerase chain reaction to determine the transcription levels of several extracellular matrix genes. RESULTS: After exogenous TGFbeta1 stimulation, both SPARC siRNA and CTGF siRNA showed a protective role against overexpression of collagen genes. Following TGFbeta1 stimulation, SPARC siRNA-transfected fibroblasts showed a greater reduction in expression of the collagen genes compared with CTGF siRNA-transfected fibroblasts, as well as a significantly decreased expression of CTGF (P < 0.05). Using linear structure equations to quantitatively model a genetic network based on expression levels of each gene, a positive regulatory role of SPARC on CTGF, COL1A2, COL3A1, COL11A1, and TIMP3 was observed. However, the regulatory role of CTGF on SPARC appeared to be negative and very small, while the positive regulatory effects of CTGF on COL1A2, COL3A1, COL11A1, and TIMP3 were less than those of SPARC. CONCLUSION: The results of this quantitative comparison support the hypothesis that in these cultured fibroblasts, the regulatory effects of SPARC on some major extracellular matrix structural components are greater than those of CTGF. In addition, SPARC appears to regulate CTGF in a predominantly positive manner, while CTGF may act as a negative feedback control on SPARC following TGFbeta stimulation.

Cells, Cultured↗

PubMed2001

[Retrospective analysis of argon laser for treating retinal periphlebitis].

OBJECTIVES: This article was to investigate the curative effect of argon laser photocoagulation for retinal periphlebitis treatment, and then to discuss the stage of the treatment. METHODS: According to the condition of vitreous hemorrhage and the range of retinal neovascularization, 31 cases (34 eyes) were divided into the light group and the heavy group, and the therapeutic effective rate, the condition of visual acuity and vitreous hemorrhage were compared. RESULTS: The therapeutic effective rate was 64.71%, there was significant difference in effective rate and prognosis of visual acuity between two groups (P < 0.01). After laser treatment, the morbidity of vitreous hemorrhage in heavy group decreased from 100% to 18.70%. CONCLUSION: Argon laser photocoagulation is an effective method for treating retinal periphlebitis and early treatment is recommended.

Adolescent↗

PubMed2001

Killing effects of ganciclovir on human pulmonary adenocarcinoma cell A549 transduced with HSV1-TK gene in vitro and in vivo.

AIM: To observe the killing effects of ganciclovir (GCV) on the human pulmonary adenocarcinoma cell A549 transduced with Herpes simplex virus I type thymine kinase (HSV1-TK) gene in vitro and in vivo. METHODS: A retroviral vector containing the TK gene was constructed and transduced into a pulmonary carcinoma cell A549 by electroporation, to observe the sensitivity of the transfected cell to GCV in vitro and the bystander effect (MTT assay). Tumor cell apoptosis caused by the TK/GCV system was observed with a flow cell meter (FCM) and a scan electronic microscope (SEM). Recombination and expression of the TK gene were examined with DNA PCR and in situ hybridization, respectively. The therapeutic effect of GCV on subcutaneous tumor growth between transfected and parental cells was also compared. RESULTS: The sensitivity of the transfected cell to GCV was 46 times higher than that of the parental cell, and the bystander effect was stronger in high cell density than in low cell density. The subG0G1 peak was shown on the DNA histogram after A549-Tk cell was treated with 50 micromol/L GCV for 3 days by FCM, but not in the A549 cell. A cell cycle analysis showed that the apoptotic cell in the A549-TK and A549 cells were (12.2+/-1.7) % and (1.3 +/- 0.3) %, respectively (P < 0.01). The cell apoptosis features of nuclear condensation, apoptotic vesicle, and nuclear showing semimoon feature were found in the A549-TK cell by SEM, but not in the A549 cell. Recombination and expression of the TK gene were positive in the transfected cell. In vivo, the growth of tumors formed by the transfected cell was apparently inhibited by GCV, but not in the control group. CONCLUSION: The transfected cell obtained sensitivity to GCV and the bystander effect was closely related to intercellular touch. The TK/GCV system killing tumor cell was related to cell apoptosis. GCV inhibited the growth of tumors which were inoculated by A549-TK cell in vivo.

Adenocarcinoma↗

PubMed2001

[Determination of bifonazole in cream by high performance liquid chromatography].

An accurate method for the determination of bifonazole in cream is described. The analytical column was packed with Hypersil ODS. The mobile phase was a mixture of 0.08 mol/L aqueous triethylamine (TEA) phosphate solution(pH 7.0)-acetonitrile-methanol (20:10:70, V/V) and the detection wavelength was 254 nm. This method is simple, accurate and can be used for the quality control of bifonazole in cream.

Antifungal Agents↗

PubMed2001

[Determination of unbound concentration of drug in drug-human serum albumin mixture by high performance frontal analysis].

A high performance frontal analysis(HPFA) method was developed to determine the unbound concentration of drugs in drug-human serum albumin (HSA) mixture under binding equilibrium. The sample was injected directly onto an internal-surface reversed-phase silica column (ISRP). The mobile phase was 67 mmol/L phosphate buffer (pH 7.4, I = 0.17 mol/L). When a large volume of sample solution under drug-HSA binding equilibrium was directly injected, the drug was eluted as a trapezoidal peak with a plateau, and the drug concentration in this region was the same as that of the unbound drug in the sample solution. The eluate of plateau region was collected and a small volume was injected onto a reversed-phase HPLC column. This HPFA-HPLC method was employed in the determination of unbound concentration in both ketoprofen (KP)-HSA and cefoperazone (CP)-HSA mixtures. The unbound concentrations of drugs obtained by using HPFA-HPLC were compared with those determined with ultrafiltration-HPLC. The effects of sample volume and flow rate of mobile phase on the plateau formation were investigated. It was found that the minimum injection volume to achieve a trapezoidal peak varied with drugs. The flow rate showed no effect on the trapezoidal peak formation. The unbound concentrations of KP and CP obtained were about the same by using HPFA-HPLC or ultrafiltration-HPLC and precisions were similar for both methods.

Cefoperazone↗

PubMed2001

[Changes in SR Ca2+-ATPase activity, Ca2+ release and uptake kinetics of diaphragm muscle after different-frequency chronic electrical stimulation of diaphragmatic nerve].

To study adaptation of rabbit diaphragm muscle after different-frequency chronic electrical stimulation, Ca(2+)-ATPase activity and Ca(2+) release-uptake kinetics of sarcoplasmic reticulum (SR) were respectively measured by detecting inorganic phosphorus ion and Furo-2 fluorescence. SR Ca(2+)-ATPase activity of the low-frequency stimulation group was significantly lower than that of the control group (P<0.0l), but it was significantly higher in the high-frequency stimulation group against control (P<0.0l). The kinetics of Ca(2+) release and Ca(2+) uptake was significantly lower in low-frequency group than that of the control (P<0.0l), but the kinetics of Ca(2+) release and Ca(2+) uptake was significantly higher than that of the control (P<0.01). It is thought that different-frequency electrical stimulation induced different adaptative changes in SR Ca(2+)-ATPase activity, and Ca(2+) release and uptake kinetics of rabbit diaphragm muscle.

Animals↗

PubMed2000

[Adaptation of diaphragm muscle strip mechanics to chronic electrical stimulation and the effect of change in extracellular Ca2+ in rabbit].

AIM: The mechanical character of diaphragm muscle after chronic electrical stimulation(CES) and effect of the extracellular Ca2+ change have not yet been explored. We wondered whether there might be great different change and effect on muscle mechanics after CES and the extracellular Ca2+ change. METHODS: The twitch tension(Pt), time to peak tension(TPT), half-relaxation time(1/2 RT), tetanic tension(Po), fatigue index (FI) and fatigue recovery index(FRI) were respectively measured in normal group and CES groups; the switch tensions of diaphragm muscle strips were observed in the standard Hank's solution and the Hank's with free Ca2+. RESULTS: There were more significant decrease in Pt, Po, FI and FRI, more significant lengthening in TPT and 1/2 RT in 10 Hz and 20 Hz groups(P < 0.01). However, there was completely opposite effect in 50 Hz and 100 Hz groups. There were more significant effect on muscle mechanics of contraction and relaxation in 10 Hz and 20 Hz groups than that in 50 Hz and 100 Hz groups when the extracellular Ca2+ changed. CONCLUSION: After CES the significantly frequency dependent were presented on mechanical character of diaphragm muscle strips, and there were more effect on diaphragm muscle mechanics in 10 Hz and 20 Hz groups when the extracellular Ca2+ was changed.

Animals↗

PubMed2000

[mRNA and protein expression of skeletal DHPR(alpha1) and RyRs in diaphragm muscle of rabbits].

To detect mRNA and protein expression of skeletal dihydropridine receptor isoform alpha1 subunit and ryanodine receptor 1 and 3 in diaphragm muscle of rabbits, the coupling mode and characteristics of Ca(2+) release were explored. Reverse transcription PCR, in situ hybridization and immunohistochemical methods were employed. A higher level of mRNA and protein expression of DHPR(alpha1) and RyR(1), and a lower level of mRNA expression of RyR(3) were found. It is suggested that the calcium release unit may consist of skeletal DHPR isoform, RyR(1) and RyR(3), and there may be two kinds of Ca(2+) release mode via conformational changes in linked proteins and Ca(2+)-induced Ca(2+) release (CICR) in diaphragm muscle of rabbits.

Animals↗

PubMed2000

[Determination of three principal components in chuanjing tablets by using high performance liquid chromatography].

Uniform design method was employed to optimize the mobile phase of HPLC in order to determine simultaneously three principal components, theophylline, amobarbital and methylephedrine hydrochloride, in Chuanjing tablet, a compound preparation for asthma and cough. The stationary phase was ODS and the optimal mobile phase composition was V (0.015 mol/L phosphate buffer containing 0.3% triethylamine, pH 4.9): V (methanol) = 35:65. The detection was performed at 215 nm and the sensitivity was time programmed for simultaneous determination of minor and major components. Caffeine was selected as the internal standard. A baseline separation was achieved within 10 min. The linear ranges for theophylline, amobarbital and methylephedrine hydrochloride were 0.03 g/L-0.20 g/L, 7.5 mg/L-50.0 mg/L and 7.5 mg/L-50.0 mg/L, recoveries 99.7%-102.6%, 98.5%-100.2% and 98.0%-102.7%, inter-day RSDs 0.23%-1.2%, 0.35%-2.5%, 0.33%-1.6% respectively. This HPLC method is rapid and accurate, and suitable for the quality control of the preparation.

Amobarbital↗

PubMed2000

[Elementary events and characteristics of calcium signalling].

There are many different elementary intracellular calcium signalling in the cell. These events appear to have a hierarchical organization depending on stimulus intensity. Low levels of stimulation activate individual channels such as the blips or quarks; The next level of organization is the puffs and sparks, which appear to be derived from small clusters of channels. At high stimulus intensities these elementary events are coordinated to give global events. These events not only present the character of Ca2+ release unit, also lead to different complex spatiotemporal organization of calcium signalling, emphasizing the hierarchical organization and local control model of calcium signalling.

Animals↗

PubMed1999

Cloning, sequencing and further characterization of acylpeptide hydrolase from porcine intestinal mucosa.

Acylpeptide hydrolase was purified to homogeneity from porcine intestinal mucosa using a seven-step procedure including ammonium sulfate precipitation, gel filtration as well as anion exchange and affinity chromatography. The specific activity of the enzyme reached 105000 nmol/mg protein per min and the purification was as high as 5500-fold. This tetrameric enzyme is composed of four apparently identical subunits, the molecular mass of which was estimated to be 75 kDa, based on the results of amino acid analysis and gel electrophoresis performed under denaturing conditions. It is likely that the NH(2)-terminal residue may be acetylated, while serine was found to be the COOH-terminal residue. The hydrolytic activity of the enzyme toward N-acetyl-L-alanine p-nitroanilide at the optimum pH value was increased twofold in the presence of the chloride anion. The K(m) value calculated from the kinetics of the hydrolysis of acetylalanyl peptides was found to be 0.7+/-0.1 mM, whereas the V(max) values decreased from 200 to 50 nmol/min per microgram of enzyme, depending on the peptidic chain lengths. The V(max) value of the synthetic substrate (250 nmol/min per microgram of enzyme) was 25-500% higher than those of the acetylalanyl peptides, depending on the peptide chain length, although the enzyme affinity was slightly lower (1.8 mM as compared with 0.7 mM). In line with data on other animal species and on various tissues, the enzyme seemed likely to be a serine protease, since it was readily inhibited by diisopropyl fluorophosphate and diethyl pyrocarbonate. A 2377-nucleotide long cDNA coding for the enzyme was isolated from pig small intestine. The deduced amino acid sequence consisted of 731 residues and showed a single different amino acid with that of the porcine liver APH, except the N-terminal amino acid which is still probably lacking.

Amino Acid Sequence↗

PubMed1999

Molecular cloning and primary structure analysis of porcine pancreatic alpha-amylase.

A cDNA library was constructed in a Uni-ZAP XR vector using mRNA isolated from porcine pancreas. A full-length alpha-amylase cDNA was obtained using a combination of library screening and nested polymerase chain reaction. Sequencing of the clone revealed a 1536-nucleotide (nt) open reading frame encoding a protein of 496 amino acid (aa) residues with a signal peptide of 15 aa. The calculated molecular mass of the enzyme was 55354 Da, in accordance with those of the purified porcine pancreatic alpha-amylase forms (PPAI and PPAII) as determined by mass spectrometry. A comparison of the deduced aa sequence with published peptidic sequences of PPAI identified a number of mismatches. The sequence of the cDNA reported here provides a sequence reference for PPA in excellent agreement with the refined three-dimensional structures of both PPAI and PPAII. No evidence for a second variant was found in the cDNA library and it is most likely that PPAI and PPAII are two forms of the same protein. The primary structure of PPA shows high homology with human, mouse and rat pancreatic alpha-amylases. The 304-310 region, corresponding to a mobile loop involved in substrate binding and processing near the active site, is fully conserved.

Amino Acid Sequence↗

PubMed1999

Cloning, sequencing and functional expression of a cDNA encoding porcine pancreatic preprocarboxypeptidase A1.

A full-length cDNA clone coding for porcine pancreatic preprocarboxypeptidase A1 (prePCPA1) was isolated from a cDNA library. The open reading frame (ORF) of the nucleotide sequence was 1260 nt in length and encoded a protein of 419 amino acids (aa). The cDNA included a short signal peptide of 16 aa and a 94 aa-long activation segment. The calculated molecular mass of the mature proenzyme was 45561 Da, in accordance with that of the purified porcine pancreatic PCPA1. The deduced aa sequence of the corresponding enzyme differed from that predicted by the three-dimensional structure by 40 aa, and showed 85% identity and 55% identity to that of procarboxypeptidases A1 and A2, respectively. Moreover the sequence was identical to that of several independent cDNA clones, suggesting that it is the major transcribed gene. No evidence for a second variant was observed in the cDNA library and PCPA2 is apparently absent from the porcine pancreas. The cDNA was expressed in Saccharomyces cerevisiae under the control of the yeast triose phosphate isomerase promoter. The signal peptide of the PCPA protein efficiently directed its secretion into the culture medium (1.5 mg.L-1) as a protein of the predicted size. The recombinant proenzyme was analyzed by immunological and enzymological methods. Its activation behavior was comparable with that of the native form and led to a 35-kDa active enzyme.

Animals↗

PubMed1998

Purification and molecular cloning of porcine intestinal glycerol-ester hydrolase--evidence for its identity with carboxylesterase.

A glycerol-ester hydrolase was purified to homogeneity from porcine intestinal mucosa using a partial delipidation method and an eight-step purification procedure. The isolation scheme used gave a 483-fold purification, resulting in a pure enzyme with a specific activity on tributyrin of 290 micromol x min(-1) x mg(-1). The molecular mass of the enzyme was estimated at 240 kDa, based on the results of size-exclusion chromatography, and at 60 kDa, as determined by SDS/PAGE analysis. The isoelectric focusing data obtained indicated that only one isoform with a pI of 5.1 was present. Complete identity was found to exist between the N-terminal sequence of the first 25 amino acid residues and that of a porcine liver carboxylesterase. A full-length cDNA coding for the enzyme was isolated from pig small intestine. We observed that the corresponding protein originally named intestinal glycerol-ester hydrolase definitely belongs to the carboxylesterase family. The deduced amino acid sequence consisted of 565 residues and showed 97% identity with that of porcine liver carboxylesterase and more than 50% identity with those of other carboxylesterases from different mammalian species.

Amino Acid Sequence↗

PubMed1996

Cyclooxygenase-2 overexpression and tumor formation are blocked by sulindac in a murine model of familial adenomatous polyposis.

Inducible cyclooxygenase (Cox-2), also known as prostaglandin H synthase 2 (PGH-2) is a key enzyme in the formation of prostaglandins and thromboxanes. Cox-2 is the product of an immediate-early gene that is expressed in response to growth factors, tumor promoters, or cytokines. Overexpression of Cox-2 is associated with both human colon cancers and suppression of apoptosis in cultured epithelia] cells, an activity that is reversed by the nonsteroidal anti-inflammatory drug, sulindac sulfide. To address the relationship between Cox-2, apoptosis, and tumor development in vivo, we studied C57BL/6J-Min/+(Min) mice, a strain containing a fully penetrant dominant mutation in the Apc gene, leading to the development of gastrointestinal adenomas by 110 days of age. Min mice were fed AIN-76A chow diet and given sulindac (0.5 +/- 0.1 mg/day) in drinking water. Control Min mice and homozygous C57BL/6J-+/+ normal littermates lacking the Apc mutation (+/+) were fed AIN-76A diet and given tap water to drink. At 110 days of age, all mice were sacrificed, and their intestinal tracts were examined. Control Min mice had 11.9 +/- 7.8 tumors per mouse compared to 0.1 +/- 0.1 tumors for sulindac-treated Min mice. As expected, +/+ littermates had no macroscopic tumors. Examination of histologically normal-appearing small bowel from Min animals revealed increased amounts of Cox-2 and prostaglandin E(2) compared to +/+ littermates. Using two different in situ techniques, terminal transferase-mediated dUTP nick end labeling and a direct immunoperoxidase method, Min animals also demonstrated a 27-47% decrease in enterocyte apoptosis compared to +/+ animals. Treatment with sulindac not only inhibited tumor formation but decreased small bowel Cox-2 and prostaglandin E(2) to baseline and restored normal levels of apoptosis. These data suggest that overexpression of Cox-2 is associated with tumorigenesis in the gastrointestinal epithelium, and that both are inhibited by sulindac administration.

Adenomatous Polyposis Coli↗

PubMed1996

[Diet effect on fiberoptic colonoscopic examination].

In order to study the diet effect on fiber colonoscopic examination, sixty patients were randomly divided into two groups. Thirty patients took food during the period of intesternal preparation, the control group were fasting, then the colonoscopic examination was taken. The result showed that taking food during the period of intesternal preparation not only has no affection on the examination but also enhanced the compliance of colonoscopic examination.

Colonoscopy↗

PubMed1995

Isozyme hybrids within the protruding third loop domain of the barley alpha-amylase (beta/alpha)8-barrel. Implication for BASI sensitivity and substrate affinity.

Barley alpha-amylase isozymes AMY1 and AMY2 contain three structural domains: a catalytic (beta/alpha)8-barrel (domain A) with a protruding loop (domain B; residues 89-152) that binds Ca2+, and a small C-terminal domain. Different parts of domain B secure isozyme specific properties as identified for three AMY1-AMY2 hybrids, obtained by homeologous recombination in yeast, with crossing-over at residues 112, 116, and 144. The AMY1 regions Val90-Thr112 and Ala145-Leu161 thus confer high affinities for the substrates alpha-D-maltoheptaoside and amylose, respectively. Leu117-Phe144, and to a lesser degree Ala145-Leu161, are critical for the stability at low pH characteristic of AMY1 and for the sensitivity to barley alpha-amylase/subtilisin inhibitor specific to AMY2.

Amino Acid Sequence↗

PubMed1994

Domain B protruding at the third beta strand of the alpha/beta barrel in barley alpha-amylase confers distinct isozyme-specific properties.

alpha-Amylases belong to the alpha/beta-barrel protein family in which the active site is created by residues located at the C-terminus of the beta strands and in the helix-connecting loops extending from these ends. In the alpha-amylase family, a small separate domain B protrudes at the C-terminus of the third beta strand of the (beta/alpha)8-barrel framework. The 80% identical barley alpha-amylase isozymes 1 and 2 (AMY1 and AMY2, respectively) differ in substrate affinity and turnover rate, CaCl2 stimulation of activity, sensitivity to the endogenous 21-kDa alpha-amylase/subtilisin inhibitor, and stability at low pH. To identify regions that confer these isozyme-specific variations, AMY1-AMY2 hybrid cDNAs were generated by in vivo homologous recombination in yeast. The hybrids AMY1-(1-90)-AMY2-(90-403) and AMY1-(1-161)-AMY2-(161-403) characterized in this study contain the 90-residue and 161-residue N-terminal sequences, respectively, of AMY1 and complementary C-terminal regions of AMY2. AMY1-(1-90)-AMY2-(90-403) comprises the 60-amino-acid domain B of AMY2 and resembles this isozyme in sensitivity to alpha-amylase/subtilisin inhibitor and its low affinity for the substrates p-nitrophenyl alpha-D-maltoheptaoside, amylose and the inhibitor acarbose. Only AMY1-(1-161)-AMY2-(161-403) and AMY1, which both share domain B, are stable at low pH. However, AMY2 and both hybrid AMY species, but not AMY1, show maximum enzyme activity on insoluble blue starch at approximately 10 mM CaCl2. Domain B thus determines several functional and stability properties that distinguish the barley alpha-amylase isozymes.

Acarbose↗