Biomedical subjects

C Xu

Publications and source records attributed to C Xu.

At least 109 records · Page 6Linked to original sources

PubMed2000

Purification, characterization, and molecular cloning of the gene of a seed-specific antimicrobial protein from pokeweed.

A small cysteine-rich protein with antimicrobial activity was isolated from pokeweed (Phytolacca americana) seeds and purified to homogeneity. The protein inhibits the growth of several filamentous fungi and gram-positive bacteria. The protein was highly basic, with a pI higher than 10. The entire amino acid sequence of the protein was determined to be homologous to antimicrobial protein (AMP) from Mirabilis jalapa. The cDNA encoding the P. americana AMP (Pa-AMP-1) and chromosomal DNA containing the gene were cloned and sequenced. The deduced amino acid sequence shows the presence of a signal peptide at the amino terminus, suggesting that the protein is synthesized as a preprotein and secreted outside the cells. The chromosomal gene shows the presence of an intron located within the region encoding the signal peptide. Southern hybridization showed that there was small gene family encoding Pa-AMP. Immunoblotting showed that Pa-AMP-1 was only present in seeds, and was absent in roots, leaves, and stems. The Pa-AMP-1 protein was secreted into the environment of the seeds during germination, and may create an inhibitory zone against soil-borne microorganisms. The disulfide bridges of Pa-AMP-1 were identified. The three-dimensional modeling of Pa-AMP-1 indicates that the protein has a small cystine-knot folding, a positive patch, and a hydrophobic patch.

Amino Acid Sequence↗

PubMed2000

Structure of xylose isomerase from Streptomyces diastaticus no. 7 strain M1033 at 1.85 A resolution.

The structure of xylose isomerase (XyI) from Streptomyces diastaticus No. 7 strain M1033 (SDXyI) has been refined at 1.85 A resolution to conventional and free R factors of 0.166 and 0.219, respectively. SDXyI was crystallized in space group P2(1)2(1)2, with unit-cell parameters a = 87.976, b = 98.836, c = 93.927 A. One dimer of the tetrametric molecule is found in each asymmetric unit. Each monomer consists of two domains: a large N-terminal domain (residues 1-320), containing a parallel eight-stranded alpha/beta barrel, and a small C-terminal loop (residues 321-387), containing five helices linked by random coil. The four monomers are essentially identical in the tetramer, possessing non-crystallographic 222 symmetry with one twofold axis essentially coincident with the crystallographic twofold axis in the space group P2(1)2(1)2, which may explain why the diffraction pattern has strong pseudo-I222 symmetry even at medium resolution. The crystal structures of XyIs from different bacterial strains, especially from Streptomyces, are similar. The alpha2 helix of the alpha/beta barrel has a different position in the structures of different XyIs. The conformation of C-terminal fragment 357-364 in the SDXyI structure has a small number of differences to that of other XyIs. Two Co(2+) ions rather than Mg(2+) ions exist in the active site of the SDXyI structure; SDXyI seems to prefer to bind Co(2+) ions rather than Mg(2+) ions.

Aldose-Ketose Isomerases↗

PubMed2000

Current methods in medical image segmentation.

Image segmentation plays a crucial role in many medical-imaging applications, by automating or facilitating the delineation of anatomical structures and other regions of interest. We present a critical appraisal of the current status of semi-automated and automated methods for the segmentation of anatomical medical images. Terminology and important issues in image segmentation are first presented. Current segmentation approaches are then reviewed with an emphasis on the advantages and disadvantages of these methods for medical imaging applications. We conclude with a discussion on the future of image segmentation methods in biomedical research.

Algorithms↗

PubMed2000

Hypercholesterolemia superimposed by experimental hypertension induces differential distribution of collagen and elastin.

We studied the mural distribution of collagen types I and III and tropoelastin in enhanced experimental atherogenesis induced in rabbits by hyperlipidemia superimposed by hypertension. Animals were fed a high-cholesterol diet for 5 weeks and also subjected to midthoracic aortic coarctation for 4 weeks. Serum cholesterol levels were increased and blood pressure was elevated proximal to the coarctation. Foam cell lesions developed in the aorta proximal to the coarctation. In situ hybridization and immunohistochemistry showed that gene expression of collagen types I and III and tropoelastin was upregulated, with a differential distribution across the arterial wall. New collagen type I was mainly distributed in the intima, the outer media, and the adventitia. New collagen type III was spread more uniformly across the wall, including the adventitia, whereas tropoelastin was mainly localized in intimal foam cell lesions. Morphometric data showed an increase in wall thickness. These results suggest that collagen types I and III play a role in remodeling of the aortic wall in response to hypertension. The remarkable involvement of the adventitia in this response indicates that the adventitia is an important component of the arterial wall. Tropoelastin is closely associated with foam cell lesion formation, suggesting a role for this component in atherogenesis as well.

Animals↗

PubMed2000

Differential transcriptional regulation of rat vasopressin gene expression by estrogen receptor alpha and beta.

Neuronal expression of vasopressin messenger RNA (mRNA) and peptide has been shown to be estrogen dependent. A 5.5-kb genomic DNA fragment, 5' of the AVP coding region, was used in luciferase reporter assays to measure transcriptional activation by either estrogen receptor alpha or beta in response to various treatments. ER alpha and ER beta displayed differential regulation of the AVP promoter. SK-N-SH cells transfected with ER alpha exhibited increased luciferase activity in response to estrogen, and the selective estrogen receptor modulators (SERMs), Tamoxifen, and ICI 182,780. Cells transfected with ER beta exhibited a high constitutive activity, which is unchanged by exposure to SERMs but can be inhibited by estrogen. Deletion of 1.5 kb from the 5' end or mutation of a single estrogen response element (ERE)-like sequence resulted in loss of estrogen-dependent induction by ER alpha and increased the ability of estrogen to inhibit the high constitutive activity of ER beta. The distal ERE-containing 1.5-kb fragment, when coupled to luciferase, is able to support both ER alpha and ER beta mediated activation of transcription by estrogen. These results suggest that a single ERE in the distal 1.5-kb portion of the 5.5-kb fragment contains the primary positive estrogen responsive sequences for ER alpha and ER beta. The data also suggest that sequences proximal to this element serve to inhibit transcription mediated by ER beta.

Animals↗

PubMed2000

The effects of recombinant RA538 and antisense c-myc adenovirus on tumor cells and the molecular mechanism concerned.

OBJECTIVE: Compare the biological effects of recombinant RA538 and antisense c-myc adenovirus on human gastric cancer cell line (SGC7901) and explore the molecular mechanism in vitro and in vivo. METHODS: SGC7901 cells were treated with Ad-RA538, Ad-AS c-myc or Ad-LacZ. MTT, DNA ladder, TUNEL and FCM, RT-PCR, Western blot analysis, the tumorigenicity in nude mice and experimental therapy of the nude mice were used. RESULTS: Ad-RA538 and Ad-ASc-myc could strongly inhibit cell growth and induce apoptosis of SGC7901 cells. The growth of the Ad-RA538- and Ad-ASc-myc-infected SGC7901 cells were inhibited by 76.3% and 44.1% respectively. The over expression of RA538 and ASc-myc could down-regulate expression of c-myc, bcl-2 and cyclinD1 gene and up-regulate expression of bax gene, but it could not regulate expression of p53, p16, TGase, and ras gene. The tumorigenicity of Ad-RA538 or Ad-ASc-myc in nude mice showed that three of three mice failed to form tumor, compared with Ad-LacZ and parent SGC7901 cells from 7 to 30 days. Experimental therapy of the nude mice bearing subcutaneous tumor of SGC7901 cells showed that intratumor instillation of Ad-RA538 and Ad-ASc-myc inhibited the growth of the tumors. Ad-RA538- and Ad-ASc-myc-treated tumors were inhibited by 60.7% or 68.9% respectively, compared with the tumor injected with Ad-LacZ and mock. CONCLUSION: The expression of Ad-RA538 and Ad-ASc-myc can inhibit growth and induce apoptosis of gastric cancer cell in vitro and in vivo. RA538 and ASc-myc relate to c-myc, bcl-2, cyclinD1 and bax gene closely and have noticeable biologic effects on gastric cancer cells.

Adenoviridae↗

PubMed2000

[Glucose isomerase gene knock-out by denatured double-stranded DNA].

After Genetic background analysis of Streptomyces diastaticus No. 7 strain M1033, the modified conditions of M1033 protoplasts and transformation were established. Replacement plasmid for homologous recombination was also constructed by inserting tsr gene into glucose isomerase gene. The homologous recombination of GI gene in M1033 chromosomes was achieved by using denatured linearized DNA fragments and glucose isomerase deficient strain M1033LJ was obtained. It is basic for introducing mutation into M1033 chromosome and realizing site-directed molecular reformation.

Aldose-Ketose Isomerases↗

PubMed2000

[Determination of fructose-1,6-diphosphate with aldolase-DNPH by the colorimetric method].

This paper presents a modified method of enzymatic assay for Fructose-1,6-diphosphate(FDP). FDP is split to dihydroxyacetone phosphate (DAP) and glyceraldehyde-3-phosphate (GAP) by the action of aldolase. DAP is hydrolyzed at room temperature to free triose. Under alkaline conditions, the free triose is reacted with 2,4-dinitrophenylhydrazine (DNPH), yielding a 2,4-dinitrophenylhydrazine derivative which dissolve in alkali forming a purple color mixture, with maximum absorption at 540.nm. It is proportional to the contents of FDP. Because the method depends on the colorimetric determination of triose formed from fructose-1,6-diphosphate only by aldolase, glycerophosphate dehydrogenase/triosephosphate isomerase (GDH/TIM) and reduced nicotinamide adenine dinucleotide (NADH) which usually applied in multienzymatic method, are omitted in the modified method. The method is specific, convenient and accuracy for the determination of FDP.

Colorimetry↗

PubMed2000

[Land use dynamic monitoring supported by remote sensing and GIS--a case study in Kenli County of Yellow River delta].

By remote sensing both visual interpretation and computer aided classification, the land use information of Kenli County of Yellow River delta in 1981, 1991 and 1995 was compared and analyzed. The unifying land use dynamic monitoring classification system was made, and the methods of land use dynamic monitoring both on land use type areas and on their spatial distribution were proposed. The changes of land use type areas of Kenli County were analyzed, and the spatial dynamics of land use types from 1981 to 1995 was analyzed under GIS support. In addition, the land use changes of outdoor monitoring plots were analyzed, and the basic patterns of land use dynamics of Kenli County were proposed.

City Planning↗

PubMed2000

Detecting residual ischemia and identifying coronary artery disease after myocardial infarction using dobutamine technetium-99m-MIBI SPECT.

OBJECTIVE: To evaluate dobutamine technetium-99m methoxy isobutyl nitrile (sestamibi) single-photon emission computed tomography (Dobu-ECT) in detecting residual ischemia and identifying coronary vessel disease after myocardial infarction. METHODS: Sixty-two patients with confirmed myocardial infarction were studied with Dobu-ECT at the time of coronary artery angiography. Dobutamine was administered intravenously in incremental rates from 5 to 40 micrograms.kg-1.min-1 at 3-minute intervals. At the highest infusion rate, 7.4 x 10(8) Bq 99mTc-MIBI was injected intravenously, and tomographic imaging was performed after one hour. Resting images were taken after 24 hours, with a second dose of 99mTc-MIBI. RESULTS: The sensitivity of Dobu-ECT in detecting residual ischemia of myocardial infarction was 76%, which was higher than dobutamine electrocardiography (Dobu-ECG). Regardless of the single-, double- or triple-vessel diseases, Dobu-ECT was superior to Dobu-ECG in identifying residual ischemia (56% vs 4%, 86% vs 27%, 100% vs 47%, P < 0.01, respectively). The incidence of residual ischemia in patients receiving thrombolytic therapy was 67%, lower than patients without thrombolysis (72%) or those with an old myocardial infarction (94%). But the differences were not statistically significant. Dobu-ECT detected only 56% of ischemias in non-infarct related myocardium. Eighty-two percent of all significantly stenosed vessels were detected with Dobu-ECT, and 84% of patients with multivessel disease could be accurately identified. The sensitivity of Dobu-ECT was significantly greater for detecting severe stenosis over moderate stenosis. The sensitivity for detecting stenosis in the right coronary artery was greater than left anterior descending or left circumflex, but its specificity was lower. CONCLUSION: Dobu-ECT can identify residual ischemia, as well as its location and extent after myocardial infarction. Dobu-ECT can also accurately detect significantly stenosed vessels.

Adult↗

PubMed2000

Multicenter clinical trial using an accelerated streptokinase regimen in patients with acute myocardial infarction.

OBJECTIVE: To observe the clinical efficacy and safety of intravenous thrombolytic therapy using an accelerated streptokinase (SK) regimen in acute myocardial infarction (AMI). METHODS: Data were collected from 40 hospitals during April 1996 to July 1997. Clinical therapeutic efficacy, five-week mortality, and adverse events were analyzed in 527 patients with AMI treated with an accelerated SK regimen (1.5 million IU within 30 min). RESULTS: The reperfusion rate of infarct-related arteries (IRAs) was 79.7% (421/528) assessed by clinical signs. The total mortality in the first 5 weeks was 6.6% (35/527). The incidence of allergic reactions and hypotension was 3.8% (20/528) and 4.2% (22/528), respectively. The incidence of bleeding was 2.7% (14/528), including cerebral bleeding 0.8% (4/528) and other major bleeding 0.8% (4/528). CONCLUSION: Intravenous accelerated SK therapy can markedly improve reperfusion rate without increasing adverse events such as bleeding, allergic reactions and hypotension.

Aged↗

PubMed2000

[Intervention treatment of hepatocellular carcinoma with 125I-lipiodol plus chemotherapeutic drugs and self body hairs: a report of 56 cases].

OBJECTIVE: To study the therapeutic effects on primary hepatic cancer of intervention treatment with a preparation consisting of 125I-iodinated lipiodol ultrafluid (LUF) plus self body hairs and cell-cycle nonspecific chemotherapeutic agents. METHODS: The treatment was given to 56 patients with primary hepatic cancer. CT, US, DSA, serum AFP determination, and urine radioactivity were carried out before and after treatment. RESULTS: The preparation was found to be held up in the end arteries supplying the tumor for a considerable length of time without passing through blood capillaries into the general circulation. It helped keep the chemotherapeutic drugs and internal radiation staying at the tumor site. The side effects of this treatment were tolerable. No rejection reaction was observed. In thirty six of the 56 patients (64.3%), the tumor reduced by 50%-70% in diameter, and in the remaining 20 patients(35.7%) the reduction in tumor diameter was less than 50% or not at all. The clinical manifestations, liver functions and serum AFP level improved in all cases. The survival rate in 6, 12, 24 and 36 months was 100%, 82.1%, 63.1% and 55.6%, respectively. CONCLUSION: The new intervention treatment for primary liver cancer herein described is easy to perform and can significantly improve survival and quality of life.

Adult↗

PubMed2000

[A comparison between latanoprost and timolol in treatment of patients with primary open-angle glaucoma and ocular hypertension].

OBJECTIVE: To evaluate the therapeutic value of latanoprost on glaucoma. METHODS: In an open-label fashion, multicenter, randomized control clinical trial, the efficacy and adverse drug reactions of topical application of 0.005% latanoprost once daily were compared with that of 0.5% timolol twice daily for 12 weeks in patients with open-angle glaucoma or ocular hypertension. RESULTS: The study included 128 patients (63 patients in latanoprost group and 65 patients in timolol group) and 117 patients remained at the end of the study (60 cases in latanoprost group and 57 cases in timolol group). Comparing 12 weeks with baseline diurnal intraocular pressure (IOP), the IOP reduction (mean +/- standard deviation) in latanoprost group was (7.5 +/- 0.3) mm Hg (1 mm Hg = 0.133 kPa) (32%, t = 22.73, P < 0.0001) greater than the reduction in timolol group (6.1 +/- 0.3) mm Hg (26%, t = 17.94, P < 0.0001), the difference between the two groups being significant (F = 9.54, P = 0.0026). Two patients treated with timolol and none treated with latanoprost were withdrawn from the study because of inadequate IOP control; 3 patients with latanoprost had foreign body sensation. In latanoprost group, there was one patient whose eyelashes became darker and longer at the last visit (the 12th week). No ocular and systemic adverse events related to the two drugs were found. CONCLUSION: It is demonstrated that 0.005% latanoprost topically applied once daily is well tolerated and more effective in reducing IOP than 0.5% timolol topically applied twice daily. Thus, latanoprost has the potential to be a new first-line antiglaucoma drug.

Adrenergic beta-Antagonists↗

PubMed2000

[Effects of oral calcium supplementation on blood pressure in population].

OBJECTIVE: To assess the effects of oral intake of calcium lactate tablet on blood pressure and serum levels of sodium, potassium, calcium and phosphors. METHODS: In a rural area with natural population with higher average blood pressure and prevalence of hypertension, and with high salt and low calcium intake in diet in Yu County, Shanxi Province, 112 volunteers aged 30 to 64 years were selected based on a mass screening for hypertension, and randomized into trial and control groups with double blinding, taking calcium lactate tablets (800 mg of calcium daily) and placebo respectively for five weeks. Ninety-eight of them complied with the medical order completely, 39 males and 59 females, and were followed-up for systolic (SBP) and diastolic blood pressure (DBP), and their fasting venous blood specimen and 8-hour nocturnal urine specimens were collected. Twenty-four-hour diet recall was obtained for three consecutive days from all of them. RESULTS: Reduction of 4.7 mm Hg (0.62 kPa) and 2.7 mm Hg (0.36 kPa) in systolic and diastolic blood pressure, respectively in the trial group was observed, as compared with that in control one, with P-values of 0.027 and 0.074, respectively, after 35 days of treatment. The higher their baseline BP level, the greater reduction of their BP after treatment. Urinary excretion of calcium increased and serum level of phosphorus reduced after oral administration of calcium. CONCLUSION: In an area with higher prevalence of hypertension and with high salt and low calcium intake in diet, change in diet composition or supplementation with calcium could reduce their average blood pressure and prevent them from hypertension for those with mild and moderate hypertension and in high risk with higher blood pressure.

Administration, Oral↗

PubMed2000

[The effects of different patterns of mechanical ventilation on the respiratory mechanics and gas exchange in dogs severely injured by steam inhalation].

OBJECTIVE: To study the effects of conventional mechanical ventilation (CMV), high-frequency jet ventilation (HFJV) and high-frequency bidirectional jet ventilation (HFTJV) on the respiratory mechanics and gas exchange in dogs inflicted severely by steam inhalation injury. METHODS: Nine mongrel dogs inflicted by steam inhalation to severe inhalation injury were served as the model. Indices of respiratory mechanics, hemodynamics and blood gas analysis were monitored respectively with the above three patterns of mechanical ventilation. RESULTS: (1) Total respiratory resistance (Rrs) and resistance of lungs (R(L)) were evidently higher with the ventilations than those in control (P < 0.01). And total respiratory compliance (Crs) and compliance of lungs (C(L)) were obviously lower with the ventilations than those in control (P < 0.05) but with no significant differences among the changes of Rrs, R(L), Crs and C(L). (2) Carbon dioxide (CO(2)) retention could be induced by CMV and HFJV. HFTJV was much more effective than HFJV in enhancing the expiration of CO(2) (P < 0.01). (3) There was no remarkable difference in functional residual capacity (FRC) and PaO2 between dogs with three patterns of ventilations. CONCLUSION: All these three patterns of ventilations could overcome the respiratory resistance and help respiration, but they couldn't restore the high airway resistance and low compliance of lungs already established postburn. The efficiency of CMV was similar to that by HFJV, but that of HFTJV was much better than that of HFJV.

Animals↗

PubMed2000

[The expression of Fas antigen and plasma levels of sFas and sFasL in patients with aplastic anemia].

OBJECTIVE: To investigate the role of Fas/FasL system in the pathogenesis of aplastic anemia (AA) and its correlation with clinical status. METHODS: Plasma levels of sFas and sFasL and the expression of Fas antigen on mononuclear cell (MNC) membrane in 32 AA patients and 24 normal controls were assayed by ELISA and FACS, respectively. RESULTS: The percentage of CD(34)(+)Fas(+) cells was significantly higher (P < 0.05) in AA patients than that in normal controls, and the percentage of CD(34)(+)Fas(+) cells in severe AA patients was much higher than that in chronic AA patients (P < 0.05). The percentage of CD(34)(+)Fas(+) cells was negatively correlated with the course of disease. The levels of sFas were significantly lower (P < 0.05) in AA patients than that in normal controls, and the sFas levels in severe AA were much lower than those in chronic AA (P < 0.05). The percentage of CD(34)(+)Fas(+) cells was negatively correlated with sFas level. CONCLUSION: Fas/FasL system aberration is involved in the pathogenesis of AA.

Adolescent↗

PubMed2000

[Diagnosis of PNH by detecting the resistance of RBCs to the hemolytic effect of hec toxin secreted by Aeromonus hydrophila].

OBJECTIVE: To study the feasibility of diagnosing paroxysmal nocturnal hemoglobinuria (PNH) with hec toxin (secreted by Aeromonus hydrophila) test. METHODS: The crude hec toxin was extracted from the culture medium of Aeromonus hydrophila by precipitating with saturated (NH(4))(2)SO(4) and then purified through DEAE52. This crude hec toxin was used to act on red blood cells (RBCs) from patients with PNH, non-PNH anemias, and normal persons. Absorbance at 630nm was measured to quantitate the extent of hemolysis. Hec treated and untreated RBCs were both stained with anti CD(59) monoclonal antibody and FITC labelled goat-anti-mouse IgG. The percentage of CD(59)(+) cells was detected by flow cytometry. RESULTS: After hec toxin treatment, RBCs from PNH patients showed resistance to the toxin hemolysis, which was negatively related to the CD(59)(+) cells percentage, while RBCs from non-PNH were lysed totally. CONCLUSION: RBCs from PNH have obvious resistance to the hemolytic effect of hec toxin, and the percentage of remained unhemolytic cells reflect the severity of PNH. Resistance detection of RBCs to hec toxin can be used for the diagnosis of PNH.

Bacterial Toxins↗

PubMed2000

[Terminal differentiation of human acute promyelocytic leukemia (APL) cells induced by Tanshinone II A in primary culture].

The aim of this study was to investigate whether Tanshinone II A (Tan II A) can induce human acute promyelocytic leukemia (APL) cells to differentiate or not in primary culture. The APL cells from 5 cases were cultured respectively with Tan II A at the concentration of 0.5 microgram/ml for 7 days in vitro. The differentiations of these leukemia cells were observed cytomorphologically and examined by nitroblue tetrazolium (NBT) test. The cell DNA cycle and membrane cluster differentiation (CD) antigens (CD33, CD11b) were analyzed by flow cytometry. The results showed that 82.5% +/- 4.8% of APL cells were induced into morphologically and functionally differentiated cells. The cell growth curve showed that the growth of APL cells was inhibited. The degree of differentiation and growth inhibition induced by Tan II A was not different from that by ATRA (P > 0.05). Flow cytometry analysis showed that Tan II A arrested APL cells in G0/G1 phase and inhibited cellular DNA synthesis. This study demonstrates that Tan II A can induce differentiation of APL cells in vitro, and hence it is worthy of further studies for clinical use.

Abietanes↗