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Biomedical subjects

Yan Zhang

Publications and source records attributed to Yan Zhang.

At least 523 records · Page 29Linked to original sources
PubMed2002

Osmoregulation and fungicide resistance: the Neurospora crassa os-2 gene encodes a HOG1 mitogen-activated protein kinase homologue.

Neurospora crassa osmosensitive (os) mutants are sensitive to high osmolarity and therefore are unable to grow on medium containing 4% NaCl. We found that os-2 and os-5 mutants were resistant to the phenylpyrrole fungicides fludioxonil and fenpiclonil. To understand the relationship between osmoregulation and fungicide resistance, we cloned the os-2 gene by using sib selection. os-2 encodes a putative mitogen-activated protein (MAP) kinase homologous to HOG1 and can complement the osmosensitive phenotype of a Saccharomyces cerevisiae hog1 mutant. We sequenced three os-2 alleles and found that all of them were null with either frameshift or nonsense point mutations. An os-2 gene replacement mutant also was generated and was sensitive to high osmolarity and resistant to phenylpyrrole fungicides. Conversely, os-2 mutants transformed with the wild-type os-2 gene could grow on media containing 4% NaCl and were sensitive to phenylpyrrole fungicides. Fludioxonil stimulated intracellular glycerol accumulation in wild-type strains but not in os-2 mutants. Fludioxonil also caused wild-type conidia and hyphal cells to swell and burst. These results suggest that the hyperosmotic stress response pathway of N. crassa is the target of phenylpyrrole fungicides and that fungicidal effects may result from a hyperactive os-2 MAP kinase pathway.

Dioxoles↗
PubMed2002

A fluorescence polarization assay for cyclic nucleotide phosphodiesterases.

Cyclic nucleotide phosphodiesterases (PDEs) catalyze the hydrolysis of the 3'-ester bond of cyclic AMP (cAMP) and cyclic GMP (cGMP), important second messengers in the transduction of a variety of extracellular signals. There is growing interest in the study of PDEs as drug targets for novel therapeutics. We describe the development of a homogeneous fluorescence polarization assay for PDEs based on the strong binding of PDE reaction products (i.e., AMP or GMP) onto modified nanoparticles through interactions with immobilized trivalent metal cations. This assay technology (IMAP) is applicable to both cAMP- and cGMP-specific PDEs. Results of the assay in 384- and 1536-well microplates are presented.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed2002

Expression and identification of recombinant soluble single-chain variable fragment of monoclonal antibody MC3.

AIM: To generate soluble single chain variable fragments (ScFv) of monoclonal antibody MC3 recognizing colorectal and gastric carcinomas. METHODS: mRNA was isolated from the hybridoma cell line producing MC3 and the DNAs encoding variable domains of heavy and light chains (VH and VL) of the antibody were amplified separately by RT-PCR and assembled into ScFv DNA with a linker DNA. The ScFv DNA was ligated into the phagemid vector pCANTAB5E and the ligated sample was transformed into E.coli TG1. The transformed cells were infected with M13KO7 helper phage to yield recombinant phages. After two rounds of panning with gastric carcinoma cell line AGS highly expressing MC3-binding antigen, the phage clones displaying ScFv fragments of the antibody were selected by ELISA. 4 phage clones showing strong signal in ELISA were used to infect E.coli HB2151 to express soluble ScFvs. The soluble ScFvs were identified by Dot blot and Western blot, and their antigen-binding activity was assayed by ELISA. The VH and VL DNAs of the ScFv DNA derived from phage clone 19 were sequenced. RESULTS: The VH,VL and ScFv DNAs were about 340 bp, 320 bp and 750 bp respectively. After two rounds of panning to the recombinant phages, 18 antigen-positive phage clones were selected from 30 preselected phage clones by ELISA. All the soluble ScFvs derived from the 4 out of the 18 antigen-positive phage clones were about M(r)32000 and concentrated in periplasmatic space under the given culture condition. The soluble ScFvs could bind the antigen, and they shared the same binding site with MC3. The sequences of the VH and VL DNAs of the MC3 ScFv showed that the variable antibody genes belonged to the IgG1 subgroup,kappa-type. CONCLUSION: The soluble ScFv of MC3 is successfully produced, which not only provides a possible novel targeting vehicle for in vivo and in vitro study on associated cancers, but also offers the antibody a stable genetic source.

Animals↗
PubMed2002

Synthesis of an enzyme-dependent prodrug and evaluation of its potential for colon targeting.

AIM: To synthesize dexamethasone-succinate-dextran (DSD) conjugate and to evaluate the potentiality of DSD for the treatment of inflammatory bowel diseases. METHODS: Dexamethasone was attached to dextran (average molecular weight=70,400 Dalton) using succinate anhydride in an anhydrous environment catalyzed by 4-dimethylaminopyridine and 1, 1'-carbonyldiimidazole. The chemical structure of DSD was identified by UV, IR and NMR, and the in vivo drug release behavior of this prodrug was investigated after oral administration of DSD suspension. RESULTS: The DSD conjugate was obtained in two steps and the content of dexamethasone in DSD was 11.28 %. The dextran prodrug was stable in rat stomach and small intestine and negligibly absorbed from these tracts. Four to nine hours after the oral administration, most of the prodrug (>95 %) had moved to the cecum and colon, and was easily hydrolyzed by an endodextranase. Recover of dexamethasone from colon and cecum after administration of DSD conjugate was 6-12 folds higher than the recovery after administration of unmodified dexamethasone (t=2.74, P<0.05). The preferential release of free dexamethasone in cecum and colon over that in the small intestine was statistically significant (t=2.27, P<0.05). CONCLUSION: The results of this study indicate that dextran conjugates may be useful in selectively delivering glucocorticoids to the colon.

Animals↗
PubMed2002

Enhancement of HCO(3)(-) permeability across the apical membrane of bovine corneal endothelium by multiple signaling pathways.

PURPOSE: In this study, the involvement of signaling pathways in the regulation of HCO(3)(-) permeability across the apical membrane of the corneal endothelium was examined. METHODS: Cultured bovine corneal endothelial cells (CBCECs) were grown to confluence on permeable membranes. Apical and basolateral sides were perfused with a HCO(3)(-)-rich Cl(-)-free Ringer's solution (28.5 mM; pH 7.5). Relative changes in apical HCO(3)(-) permeability were assayed by pulsing the apical perfusion bath with a low-HCO(3)(-) Cl(-)-free Ringer's solution (2.85 mM; pH 6.5), in the presence or absence of agonists or inhibitors, and comparing the rates of change in intracellular pH (pH(i)), as measured with a pH-sensitive dye. Ca(2+)-activated signaling was measured with the Ca(2+)-sensitive dye Fura-2. Qualitative changes in membrane potential (E(m)) were measured with a voltage-sensitive dye. RT-PCR using calcium-activated chloride channel (CLCA)-specific primers was used to examine the expression of CLCA in the corneal endothelium. RESULTS: The adenoceptor agonist adenosine (20 M) enhanced HCO(3)(-) permeability by a factor of 2. Forskolin (40 microM) exerted a 6.3-fold increase of HCO(3)(-) permeability, which was inhibited by the Cl(-) channel blockers, glibenclamide (50 microM) and niflumic acid (100 microM). Adenosine triphosphate (ATP) and ATPgammaS, P(2) receptor agonists that increased intracellular Ca(2+) in corneal endothelium, enhanced HCO(3)(-) permeability by 87% and 79%, respectively. ATPgammaS induced depolarization of the E(m), consistent with anion channel activation, rather than activation of Ca(2+)-dependent K(+) channels, which could secondarily increase extrusion of anions by E(m) hyperpolarization. Cyclopiazonic acid (CPA), an endoplasmic reticulum (ER) Ca(2+)-pump inhibitor that increased [Ca(2+)](i), also enhanced HCO(3)(-) permeability by 95%. Both the calmodulin kinase II (CaMKII) inhibitor KN-62 and the PKC inhibitor bisindolylmaleimide I (BIMI), decreased HCO(3)(-) permeability induced by ATPgammaS. The PKC activator PMA also increased HCO(3)(-) permeability by a factor of 1.8. RT-PCR using CLCA-specific primers showed the expression of CLCA1 in both fresh and cultured BCECs. CONCLUSIONS: Activation of adenoceptors and purinoceptors enhances HCO(3)(-) permeability across the apical membrane of the cultured corneal endothelium. Multiple signaling pathways (PKA, PKC, and Ca(2+)/CaMKII) contribute to the HCO(3)(-) transport in cultured corneal endothelium. Both cAMP and Ca(2+)-activated Cl(-) channels (possibly CLCA) may be involved in HCO(3)(-) transport.

Animals↗
PubMed2002

[Changes in extracellular matrix of endothelial cells co-cultured with VSMC under shear stress].

The construction and amount of fibronectin (Fn), laminin (Ln) and collagen type IV (ColIV) in the extracellular matrix of endothelial cells (EC) co-cultured with vascular smooth muscle cells (VSMC) under shear stress were studied by immuno-fluoro-cytochemistry, laser confocal scanning microscopy and image analysis methods to detect the effect of shear stress on adhesion of EC for vascular tissue engineering. One group of EC was maintained under static conditions as a control. In the control, both Fn and Ln exhibited as a granular pattern in perinuclear area and a fibrillar pattern localized underneath EC, and Col IV exhibited mainly as the granular in the perinuclear area, but the fibrillar was fewer. On exposure of EC to shear stress in physiological range, Fn grouped into fibril tracts, and there was a tendency for some of these tracts of fibrils to align with direction of shear stress. Ln and Col IV also grouped into fibril tracts, which, in contrast to Fn, were randomly oriented, Simultaneously, all contents of the extracellular matrix had different quantitative alterations. These results suggest that the capability of adhesion of EC co-cultured with VSMC may be strengthened under shear stress.

Animals↗
PubMed2002

Left ventricular long-axis changes in early diastole and systole: impact of systolic function on diastole.

Impaired long-axis motion is a sensitive marker of systolic myocardial dysfunction, but no data are available that relate long-axis changes in systole with those in diastole, particularly in subjects with diastolic dysfunction and a 'normal' left ventricular (LV) ejection fraction. A total of 311 subjects (including 105 normal healthy volunteers) aged 20-89 years with variable degrees of systolic function (LV ejection fraction range 0.15-0.84) and diastolic function were studied using tissue Doppler echocardiography and M-mode echocardiography to determine mean mitral annular amplitude and peak velocity in systole and early and late diastole. The LV systolic mitral annular amplitude (S(LAX), where LAX is long-axis amplitude) and peak velocity (S(m)) correlated well with the respective early diastolic components (E(LAX) and E(m)) and late diastolic (atrial) components (A(LAX) and A(m)). A non-linear equation fitted better than a linear relationship (non-linear model: S(LAX) against E(LAX), r(2)=0.67; S(m) against E(m), r(2)=0.60; S(LAX) against A(LAX) and S(m) against A(m), r(2)=0.42). After adjusting for age, sex and heart rate, linear relationships of early diastolic (E(LAX), r(2)=0.70; E(m), r(2)=0.60) and late diastolic (A(LAX), r(2)=0.61; A(m), r(2)=0.64) long-axis amplitudes and velocities with the respective values for S(LAX) and S(m) were found, even in those subjects with apparently 'isolated' diastolic dysfunction. Long-axis changes in systole or diastole did not correlate with Doppler mitral velocities. We conclude that ventricular long-axis changes in early diastole are closely related to systolic function, even in subjects with diastolic dysfunction. 'Pure' or isolated diastolic dysfunction is uncommon.

Adult↗
PubMed2002

[Genetic analysis on restorer genes of D2-type CMS lines of common wheat].

On the basis of genetic characters of D2-type CMS lines, restorer lines Yi4060, M8003, 6D/6R, GR1, 960789, Bao769-22-1 et al. were gained from crossing selection. The results of genetic analysis of F2, F1BC1 population and allelic analysis of restorer genes, successive selection of self fertility from F1 showed that fertility restoration of these restorer lines was controlled by two pair independent major-genes(dominant) and different-dosage minor genes. Authors proposed that the two pair independent major-genes should be designated as D2Rf1 D2Rf1, D2Rf2 D2Rf2. The model C2(major genes + minor genes) should be first selected in breeding restorer line.

Genes, Plant↗
PubMed2002

[Association between alpha-1-antichymotrypsin gene polymorphism and cerebral hemorrhage].

OBJECTIVE: To explore the association between alpha-1-antichymotrypsin (ACT) gene A/T polymorphism and cerebral hemorrhage among Chinese people. METHODS: The DNA of peripheral leucocytes was extracted from 220 patients with cerebral hemorrhage and 276 controls. PCR- RELP was used to determine the ACT gene polymorphism. Multiple Logistic regression was performed to explore the risk factors for cerebral hemorrhage. RESULTS: After adjusting age, gender, alcohol drinking, smoking, education,history of diabetes mellitus and primary hypertension, the analysis showed: (1) the ACT AT and TT genotypes increased the risk of cerebral hemorrhage (OR = 2.33 and 2.17 respectively, P < 0.05), but were not associated with primary hypertension. Such association was more prevalent in hypertensive cerebral hemorrhage. (2) Primary hypertension significantly increased the risk of cerebral hemorrhage (OR = 8.17 P = 0.000). (3) A significant gene environment interaction, super multiplicative type 4 interaction, was shown between both ACT AT and TT genotypes and primary hypertension with an interaction index (r) value of 2.84 and an OR value of 15.92. A significant additive type 3 gene-environment interaction was shown between both ACT AT and TT genotypes and diabetes mellitus with an OR value of 2.89. CONCLUSION: ACT gene polymorphism and primary hypertension are both independent risk factors of cerebral hemorrhage. The ACT AT and TT genotypes show a significant gene-environment interaction, however, of different types, with both primary hypertension and diabetes mellitus in the occurrence of cerebral hemorrhage.

Adult↗
PubMed2002

[A comparative study on life-form spectra of evergreen broad-leaved forest in different successions in Jinyun Mountain].

The life-form of plant communities in different succession stages in Jinyun Mountain was studied and the life-form spectrum was established. The results showed that according to the characters of life-form of plant communities, the vegetation in Jinyun Mountain belonged to typical subtropical evergreen broad-leaved forest vegetation. Evergreen phaenerophytes were absolutely dominant in the life-form spectrum and its quantity accounted for more than 80%. Among phaenerophyte, quantity of microphanerophyte was the most, and quantities of mesophanerophtye and nanophanerophyte were less. Different successions had different life-form spectra. With the development of succession, the percentage of phaenerophytes increased, and other life-forms decreased correspondingly. According to the development of life-form and comparative analysis of environmental factors in different succession stages, coniferous species would be replaced by evergreen phaenerophytes.

China↗
PubMed2002

[Studies on fertility genes and its genetic characters in D2-type CMS lines of common wheat].

The kinds of fertility genes and its genetic characters for D2-type CMS lines of common wheat were studied, the results showed: (1) For D2-type CMS line, there was wide restoring sources and high digree of restoration in common wheat varieties (the restoring degree of 33.61% varieties exceeded 50%), and new CMS lines were easily bred (25.21% varieties could maintain male sterility). These characters indicated that D2-type CMS line was higher value in applied study, compared with T, K, V-type CMS lines. (2) There were two forms of nuclear genotype for D2-type CMS lines, namely A1(sterile gene) and A2(sterile gene + inhibiting gene). In nucleus of restorer lines, the fertility genotype was conditioned by 6 forms: C1(major restorer gene), C2(major restorer gene + minor restorer gene), C3(minor restorer gene), C4(major restorer gene + inhibiting gene), C5(major restorer gene + minor restorer gene + inhibiting gene), C6(minor restorer gene + inhibiting gene). The genetic expression of fertility genes was affected by environmental factors. The basic model of effective combination was A1 + C1, A1 + C2, A2 + C2. (3) The allelic restorer-genes were characterized by incomplete dominance and the nonallelic restorer-genes were characterized by additive effect, which was the important basis of breeding good restorer lines.

Fertility↗
PubMed2002

[Mutational analysis of MECP2 gene in Rett syndrome].

OBJECTIVE: To investigate mutations of MECP2 gene in classical sporadic Rett syndrome (RTT) patients in China. METHODS: Polymerase chain reaction, single strand conformation polymorphism, cloning and direct sequencing were employed to analyse the three exons of MECP2 gene in 26 RTT patients and their parents, and in 2 sisters of 2 of the RTT patients. RESULTS: Nine different mutations in exon 3 were identified in 14 of the 26 patients with RTT, including 3 missense mutations, 3 nonsense mutations, and 3 frame-shift mutations (2 deletion mutations and 1 insert mutation); 2 of these were novel. A missense variant was also identified, which was carried by unaffected father and affected daughter. CONCLUSION: Mutations in MECP2 gene were found over 50% of patients with RTT in China.

Base Sequence↗
PubMed2002

[Experimental study of K562 cell apoptosis induced by harringtonine].

OBJECTIVE: To elucidate the mechanism by which harringtonine (HT) induces apoptosis in K562 cell line. METHODS: By means of cell morphology, DNA gel electrophoresis and flow cytometry, we explored the action of HT on K562 cell line. Further study of the changes in bcr/abl gene expression was conducted using reverse transcriptase (RT)-PCR. RESULTS: HT induced apoptosis of K562 cells at the concentrations ranging from 0.01 to 100 microg/ml, exhibiting dose- and time-dependent increase in apoptotic ratios of the cells subjected to the treatment courses of 12 to 60 h. RT-PCR showed that bcr/abl gene expression was down-regulated after K562 cells had been treated with 10 microg/ml HT. CONCLUSION: Low concentration of HT can induce apoptosis in K562 cell line, possibly through the down-regulation of bcr/abl gene expression.

Antineoplastic Agents, Phytogenic↗
PubMed2002

Treatment of corneal epithelial in-growth after excimer laser in situ keratomileusis.

OBJECTIVE: To evaluate efficacy of photo therapeutic keratectomy (PTK) on corneal epithelial growth under the lamellar flap after excimer laser in situ keratomileusis (LASIK). METHODS: In the 6 eyes with epithelial in-growth, the corneal cap was lifted, and the in-growing epithelium was removed from the interface. Five to 10 pulses of PTK being 7 mm in diameter were placed over the undersurface of the flap and the stromal bed, irrigation between the interface and replacing corneal flap were performed, and 50 to 75 pulses PTK being 3 mm in diameter were utilized to smooth the flap edge. The follow-up period ranged from 5 to 12 months. RESULTS: In the follow-up, no epithelial implantation reoccurred in these 6 eyes. The uncorrected visual acuity achieved their best preoperative corrected visual acuity. CONCLUSION: The results indicate that PTK can prevent recurrent epithelial in-growth after LASIK.

Cornea↗
PubMed2002

Fractionated-clamping for thoracoabdominal aortic aneurysm repair: a modified Crawford technique.

OBJECTIVE: To apply fractionated-clamping for repair of thoracoabdominal aortic aneurysm (TAA), and evaluate its effects in decreasing surgical mortality and severe complications, such as renal failure and paraplegia, a modified crawford procedure were prospectively evaluated. METHODS: Using modified shunting and cross-clamping techniques, modified Crawford repair in 13 thoracoabdominal aorta patients were performed in the Vascular Division at Peking Union Medical College Hospital. TAA Crawford classification: 1 type I, 2 type II, 2 type III and 3 type IV TAA. Debakey classification: 1 type I, 4 type III (including 2 ruptured aneurysms), and 1 aortic coarctation. RESULTS: Thirteen procedures were performed successfully. One died of ventricular fibrillation just before completing the operation. Surgical mortality rate was 7.7% (1/13). Postoperative complications included 1 acute necrotic pancreatitis, 1 ARDS, 1 paraplegia, 1 acute renal failure, and 2 thoracic cavity bleeding. Total complication rate was 53.8% (7/13). CONCLUSIONS: Fractionated-clamping in thoracoabdominal aortic aneurysm repair is our modified Crawford procedure and aortic bypass. Clinical results demonstrate that our procedure decreased surgical mortality and major complication rate, and also alleviated viscera ischemic injury. Fractionated-clamping in aorta replacement is a practical procedure for TAA repair under general anesthesia at normal temperature.

Adult↗
PubMed2002

[Advance in researches on vegetation cover and management factor in the soil erosion prediction model].

Vegetation cover and land management are the main limiting factors of soil erosion, and quantitative evaluation on the effect of different vegetation on soil erosion is essential to land use and soil conservation planning. The vegetation cover and management factor (C) in the universal soil loss equation (USLE) is an index to evaluate this effect, which has been studied deeply and used widely. However, the C factor study is insufficient in China. In order to strengthen the research of C factor, this paper reviewed the developing progress of C factor, and compared the methods of estimating C value in different USLE versions. The relative studies in China were also summarized from the aspects of vegetation canopy coverage, soil surface cover, and root density. Three problems in C factor study were pointed out. The authors suggested that cropland C factor research should be furthered, and its methodology should be unified in China to represent reliable C values for soil loss prediction and conservation planning.

China↗
PubMed2002

[Expression of vascular endothelial growth factor in bone marrow cells of patients with acute myeloid leukemia].

OBJECTIVE: To investigate the role of vascular endothelial growth factor (VEGF) in the pathogenesis and progression of acute myeloid leukemia (AML). METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) was employed for VEGF mRNA detection. VEGF levels in the bone marrow cell cultural supernatant and plasma from normal subjects and AML patients were determined by enzyme-linked immunosorbent assay (ELISA). RESULTS: VEGF mRNA expression was present in most of the AML cell lines HL-60, K562 and Raji, but not in Jurkat cells. The expression rate of VEGF mRNA in the bone marrow cells from AML patients (82%) was higher than the rates in normal subjects (30.76%) and AML patients with autologous bone marrow transplantation (41.67%). Refractory and non-refractory AML patients had higher mean plasma VEGF levels than the normal donors and AML patients with transplantation did, without significant differences observed in the latter 2 groups. With also significant difference between them, refractory and non-refractory AML groups had respectively 11.0 and 7.3-fold higher VEGF levels in the culture supernatant than the normal donor group did. CONCLUSION: The abnormality of VEGF expression may play an important role in the development of AML, and VEGF expression might be used as one of the indexes for prognostic assessment for AML patients.

Acute Disease↗