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Biomedical subjects

X Xia

Publications and source records attributed to X Xia.

At least 73 records · Page 4Linked to original sources
PubMed1999

Inhibition of adipose differentiation by phosphatidylinositol 3-kinase inhibitors.

Phosphatidylinositol (PI) 3-kinase plays an important role in various cellular signaling mechanisms in several cell systems. The role of PI 3-kinase in adipose differentiation was investigated. For this purpose, we examined the effect of specific inhibitors of PI 3-kinase on the differentiation of two adipogenic cell lines, 1246 and 3T3-L1. The results show that two structurally different inhibitors of PI 3-kinase, i.e., LY294002 and wortmannin, blocked adipose differentiation in a time and dose-dependent fashion. The results from time- course studies indicated that PI 3-kinase activity is most important in the early phase (day 4 to day 6) of the differentiation program. The effect of PI 3-kinase inhibitor on the expression of the peroxisome proliferator-activated receptor (PPAR) gamma, a master regulator in adipogenesis induced during the differentiation process, was also examined. LY294002 significantly inhibited the induction of PPARgamma mRNA expression. During the initiation phase of adipogenesis (day 4 to day 6), the expression of PPARgamma was induced and LY294002 blocked the increase of expression of PPARgamma mRNA. The inhibition of expression of PPARgamma may provide a molecular mechanism for the action of PI 3-kinase inhibitors on adipose differentiation.

3T3 Cells↗
PubMed1999

Response of Djun and Dfos mRNA abundance to signal transduction pathways in cultured cells of Drosophila melanogaster.

The mammalian proto-oncogenes c-jun and c-fos are situated at the end of multiple signal transduction pathways and activation of their products Jun and Fos, components of the transcription factor AP-1, are able to regulate gene transcription in response to extracellular stimuli. Djun and Dfos, the products of the Drosophila proto-oncongenes Djun and Dfos, are similar in size and sequence to their mammalian counterparts c-Jun and c-Fos and are related to their mammalian counterparts by their antigenic properties. However, very little is known about how they are regulated through signal transduction pathways. This paper has investigated the response of their mRNA abundance levels to three signal transduction pathways in Drosophila cultured cells. Various agonists and antagonists that stimulate and inhibit specific enzymes in the pathways have been tested. The results suggest that Djun and Dfos mRNA are continuously expressed and their abundance levels are transiently regulated by multiple signaling pathways, the peak response coming at 1-2 hours after perturbation. Dfos is more highly regulated than Djun which is only modulated. The receptor tyrosine kinase pathways positively regulate Dfos and Djun. The cAMP-mediated pathway positively regulates Dfos but negatively regulates Djun. The protein kinase C-activated pathway does not affect Djun whereas it negatively regulates Dfos.

Animals↗
PubMed1999

Protein structure prediction in a 210-type lattice model: parameter optimization in the genetic algorithm using orthogonal array.

We have applied the orthogonal array method to optimize the parameters in the genetic algorithm of the protein folding problem. Our study employed a 210-type lattice model to describe proteins, where the orientation of a residue relative to its neighboring residue is described by two angles. The statistical analysis and graphic representation show that the two angles characterize protein conformations effectively. Our energy function includes a repulsive energy, an energy for the secondary structure preference, and a pairwise contact potential. We used orthogonal array to optimize the parameters of the population, mating factor, mutation factor, and selection factor in the genetic algorithm. By designing an orthogonal set of trials with representative combinations of these parameters, we efficiently determined the optimal set of parameters through a hierarchical search. The optimal parameters were obtained from the protein crambin and applied to the structure prediction of cytochrome B562. The results indicate that the genetic algorithm with the optimal parameters reduces the computing time to reach a converged energy compared to nonoptimal parameters. It also has less chance to be trapped in a local energy minimum, and predicts a protein structure which is closer to the experimental one. Our method may also be applicable to many other optimization problems in computational biology.

Algorithms↗
PubMed1999

[The clinical and biological significance of megakaryocytic antigen expression in acute myeloid leukemia].

OBJECTIVE: To explore megakaryocytic (MK) antigen expression in previously untreated adult acute myeloid leukemia (AML) and its relation to the clinical and biological characteristics. METHODS: Two hundred and eleven cases of AML were detected with flow cytometric immunofluorescence assay. RESULTS: Twenty-seven cases (12.8%) were MK antigen positive with the higher positive rates in hybrid acute leukemia (45.5%) and acute monoblastic leukemia (24.1%). MK antigen expression was significantly correlated with CD34 antigen expression, high white cell count, high P-glycoprotein positivity and had no correlation with chromosome aberration. 33.3% of MK positive AML patients achieved complete remission which was significantly lower than that (71.9%) in MK negative cases. CONCLUSION: MK antigen positive AML might derived from malignant transformation of hemotopoietic stem cell at earlier stage and the detection of MK expression was of values in predicting treatment effect and prognosis for adult AML.

Adolescent↗
PubMed1999

[Immunophenotype and P-glycoprotein expression in CD7 positive adult acute myeloid leukemia].

OBJECTIVE: To study the immunophenotype and P-glycoprotein expression in CD7 positive adult acute myeloid leukemia (CD7+ AML). METHODS: Morphology, P-glycoprotein, cytogenetics and immunophenotype were examined in 30 previously untreated CD7+ AML patients. RESULTS: The CD7 positive rate was 11.4% in 262 AML patients. CD7+ AML patients had a significantly higher incidence of peripheral leukocytosis and blasts and FAB M1 subtype and were associated with CD34 and P-glycoprotein expression. 42.3% of CD7+ AML achieved complete remission with a median remission duration of 4 months, and a median time to CR of 48 days. CONCLUSION: Patients with CD7+ AML are usually CD34 and P-glycoprotein positive. These patients had a lower CR rate and a shorter remission duration.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

[Cephalometric analysis of the craniofacial bony structures in patients with obstructive sleep apnea].

OBJECTIVE: To explore the craniofacial bony structure abnormalities and their possible contributions to the apneic severity in patients with obstructive sleep apnea (OSA). METHODS: One-night polysomnographic examination and a lateral cephalogram were performed in 102 male OSA patients and 37 healthy men. Sixteen variables representing craniofacial angle, distances and areas were measured by a computer software (NIH Image). RESULTS: Compared with normal subjects, OSA patients presented with: a shortened cranial base (71 +/- 4) mm: (74 +/- 3) mm, (P < 0.001), maxillum (52 +/- 5) mm: (55 +/- 4) mm, (P < 0.01), mandible (74 +/- 5) mm: (77 +/- 6) mm, (P < 0.05) and bony nasopharygeal airway dimensions, a more inferiorly and anteriorly placed hyoid bone, and retrognathia deformity. Multiple stepwise regression analysis disclosed that maxilla deficiency, retrognathia and hyoid bone misposition were important contributing factors to the apneic severity (R2 = 0.447, F = 15.471, P < 0.0001). CONCLUSIONS: OSA patients had certain craniofacial bony structure defects and cephalometric analysis of these defects is useful both in the investigation of the pathogenesis and the selection of an optimel treatment modality for each OSA patients.

Adult↗
PubMed1999

[Clinical analysis of 96 cases with pulmonary disease caused by nontuberculous mycobacteria].

OBJECTIVE: To study the clinical characteristics of nontuberculous mycobacteria (NTM) pulmonary disease. METHODS: Ninety-six out of 173 cases with NTM pulmonary disease diagnosed through identification of mycobacterium strains isolated from 5,592 sputum acid-fast staining positive cases from 1981-1996 were selected, and a retrospective analysis was made. RESULTS: According to Runyon classification, there were 14 cases with M. kansasii and 1 with M. marinum in type I, 4 with M. scrofulsceum in type II, 23 with M. intracellulare or M. avium in type III, 24 with M. chelonae and 30 with M. fortuitumin in type IV. Cases whose courses of disease were more than 10 years accounted for 31%. Main clinical symptoms included cough (78%), expectoration (71%), haemoptysis (58%) and fever (26%). Fifty-seven percent cases in X-ray chest film were seen lesions bilaterally, 42% in one side, 27% in the right and 15% in the left. One percent showed no obvious lesion in X-ray chest film. Excluding one case with incomplete data, the total resistance rate of NTM was 96% in other 95 cases, 93% in type I, 50%, 100% and 100% in type II, III, IV respectively. After antituberculous chemotherapy, sputum negative conversion was seen in 14 of 15 cases with type I NTM, 6 of 23 with type III and 14 of 54 with type IV, while definite data in 4 cases with type II were not available. CONCLUSIONS: NTM pulmonary disease is characterized by long course of disease, nonspecific symptoms, high resistance rate and unsatisfactory therapeutic efficacy.

Adult↗
PubMed1999

[A clinical study on vaccine of Mycobacterium vaccae in treating pulmonary tuberculosis].

OBJECTIVE: To study the effect of vaccine of Mycobacterium vaccae on cell-mediated immunity and on treating patients with pulmonary tuberculosis. METHODS: Seventy cases of pulmonary tuberculosis with smear positive and initial treatment were classified randomly into group I (35 cases) and group II (35 cases), receiving 2HRZS/4HR and 2HRZS/4HR plus vaccine of Mycobacterium vaccae regimens respectively. Thirty-one multi-drug resistant pulmonary tuberculosis cases were classified into group III, receiving 4 - 6 sensitive antituberculous drugs and vaccine of Mycobacterium vaccae. Improvement of clinical symptoms, resolution of pulmonary lesions, negative conversion of sputum and changes of immunological functions were observed. RESULTS: No significant difference in improvement of symptoms was found in group I and group II (P > 0.05), and the improvement rate of clinical symptoms in group III was found more than 50%. X-ray resolution rates in 4th month were 83% and 89%, and cavity reducing rates 40% and 50% respectively in group I and group II, and no significant differences were found (P > 0.05). X-ray resolution rate was 29%, cavity reducing rate 7% and no deteriorated case was found in group III. Sputum negative conversion rates in 1st, 2nd, 3rd and 4th month were 23%, 51%, 83% and 97% respectively in group I, while 31%, 77%, 89% and 100% in group II, and 3%, 16%, 29% and 32% in group III. Significant difference was found between group I and group II in sputum negative conversion rate in 2nd month after treatment (P < 0.05). After treatment, values of lymphocyte transformation test (LTT), CD(3), CD(4) and CD(4)/CD(8) of the above 3 groups were all higher than that before the treatment (P < 0.05), level of tumor necrosis factor decreased in group II and IL-2, IL-6 increased in group III. CONCLUSIONS: Vaccine of Mycobacterium vaccae is a good immunotherapy preparation, which promotes sputum negative conversion and activation of cell-mediated immunity.

Adolescent↗
PubMed1999

[Retreatment after excimer laser photorefractive keratectomy].

OBJECTIVE: To evaluate the efficacy and safety of reoperation of residual myopia because of regression, undercorrection with or without coexisting severe corneal haze after excimer laser photorefractive keratectomy (PRK). METHODS: A VISK 20/20 excimer laser was used to treat myopia of -1.00 to -16.50 diopters (spherical equivalent) at corneal plane. 35 patients (51 eyes) who had residual myopia because of regression, undercorrection with or without coexisting severe corneal haze after initial PRK were retreated by using PRK and phototherapeutic keratectomy. RESULTS: At 12 months after retreatment, the rates of uncorrected visual acuity more than or equal to 10/20 or 20/20 were 82.6% and 39.1% respectively, 100.0% and 50.0% in myopia up to -6.00 D, 73.3% and 33.3% in myopia of -6.25 to -16.50 D respectively. 86.3% of eyes were within +/- 1.00 diopters of desired emmetropia. Corneal haze after retreatment was not greater than that observed after initial procedures. CONCLUSIONS: The residual myopia because of regression, undercorrection with or without severe corneal haze after initial PRK can be successfully retreated. Although the therapeutic result of retreatment of PRK is less successful than that of the initial procedure, retreatment appears to enhance it.

Adult↗
PubMed1999

[Author analysis of papers published in "Space Medicine & Medical Engineering" from 1988 to 1998].

Objective. To probe into the characteristics of authors, institutes and region distribution of papers published in "Space Medicine & Medical Engineering" (SMME), as well as its papers indexed and cited by CBMDisc, CB-ISITC and CSCD-CD98; to look into its core authors, core regions and core institutes. Method. Bibliometric method was used to analyse its published papers, cited papers and indexed papers. Result. 716 papers have been published in SMME, among which 622 were coauthor papers (86.9%); 94 were single author papers (13.1%); organization collaboration papers 109 (15.2%); institutes 548 (76.5%); colleges and Universities 132 (18.4%); hospitals 36 (5.1%). CBMDisc and CB-ISTIC index rate were 81% and 75% of its papers respectively, SMME's 39 papers were cited in 25 journals via CSCD-CD98, 10 of 42 core authors are cited. Conclusion. Papers published in SMME per issue have been increasing in 10 years, core region is Beijing. Core authors have been formed in SMME. Papers indexed by CBMDisc and CB-ISTIC are also increasing. But its citation status is not ideal, and high cited papers and high cited authors are few. Numbers and types of Natural Scientific Foundation supported papers are increasing.

Academies and Institutes↗
PubMed1999

[Simultaneous determination of tungsten, molybdenum and titanium by k-factor dual-wavelength standard addition method].

In this paper, a new method for simultaneous spectropthotometric determination of tungsten, molybdenum and titanium is proposed. The method is based on the difference of absorption spectra of the three elements forming coloured complexes with PF in acidic medium and in the presence of nonionic surfactant Tween-80. The absorbance of sample was measured at wavelengths of 503, 530 and 560 nm, and the data were treated by the principle of the k coefficients and dual-wavelength standard addition method. The method has been applied to the determination of tungsten, molybdenum and titanium in steels, and satisfactory results were obtained.

English Abstract↗
PubMed1998

A gas chromatographic method for the sugar analysis of 3,6-anhydrogalactose-containing algal galactans.

This paper describes a new gas chromatographic method for the compositional analysis of algal galactans containing 3,6-anhydrogalactose, which is readily destroyed in usual acid hydrolysis and methanolysis. Mercaptolysis of galactans was carried out under an anhydrous condition using the newly developed solvent system, an ethanethiolic HCl solution which had been prepared by blowing dry HCl gas into ethanethiol. By heating galactans in 0.5 N HCl/ethanethiol at 60 degrees C for 12 h, component sugars including 3,6-anhydrogalactose were released quantitatively as their diethyl mercaptals. The monosaccharide diethyl mercaptals were trimethylsilylated and analyzed by gas-liquid chromatography. Each component monosaccharide was detected as a single peak since neither anomeric nor structural isomers can be produced by mercaptolysis. Furthermore, the solvent system was improved by the addition of methanol in a ratio (2/1, v/v) of ethanethiol to methanol. Heating of galactans at 60 degrees C in 0.5 N HCl/[ethanethiol:methanol (2/1, v/v)] released more rapidly and quantitatively monosaccharide diethyl mercaptals without any formation of monosaccharide methyl glycosides. The present method was applicable to not only algal galactans but also algal powders.

Carbohydrate Sequence↗
PubMed1998

Pea polyubiquitin genes: (I) structure and genomic organization.

Four polyubiquitin genes, PUB1, PUB2, PUB3 and PUB4, were isolated from a pea (Pisum sativum L. cv Alaska) genomic library and completely sequenced. They represent all of the four polyubiquitin genes of the ubiquitin gene family in pea. The coding regions of the genes contain five or six coding units arranged as tandem repeats. The different coding repeats of the four genes share homologies between 75 and 97%, encoding the same protein of 76 amino acids identical to those from other higher plants. The open reading frames of PUB1, PUB2 and PUB4 terminate in the additional amino acid, phenylalanine (F), and PUB3 terminates in isoleucine (I). The polyubiquitin genes all contain intron sequences ranging from 584 to 1114 bp immediately 5' to the ATG initiation codon of the first coding sequence. Of the four genes, three are associated with long AT-rich (85.4-89.4% A+T) sequences ranging from about 331 to 478 bp at their 5' or 3' ends. The PUB4 gene was found to be linked to a moderate to highly repetitive DNA at its 5' flanking sequence. The greater sequence homology between different genes than among individual repeating units of a gene suggests that the polyubiquitin genes may have arisen by gene duplication of a single gene sequence.

Amino Acid Sequence↗
PubMed1998

Identification of cell surface binding sites for PC-cell-derived growth factor, PCDGF, (epithelin/granulin precursor) on epithelial cells and fibroblasts.

PC cell derived growth factor (PCDGF) is an 88-kDa glycoprotein purified from the culture medium of the highly tumorigenic mouse teratoma-derived cell line PC. PCDGF was shown to stimulate the proliferation of 3T3 fibroblasts and PC cells. Amino acid sequencing of PCDGF indicated its identity to the precursor for the 6-kDa polypeptides epithelins and granulins. In this paper, we investigated the binding of PCDGF to the mink lung epithelial cell line CCL64. Scatchard analysis indicates that 125I-PCDGF binding to CCL64 cells is curvilinear, corresponding to the existence of two classes of binding sites: high affinity binding sites (560 +/- 170 sites/cell) with a Kd1 of 43 +/- 15 pM and low affinity binding sites (16,350 +/- 5900 sites/cell) with a Kd2 of 3.9 +/- 1.9 nM. 125I-PCDGF was chemically crosslinked to cell surface receptors on CCL64 cells with disuccinimidyl suberate. A major crosslinked band of about 190 kDa with radiolabeled PCDGF was detected after SDS-PAGE, suggesting the presence of PCDGF binding sites with molecular weight of about 120 kDa. 125I. PCDGF crosslinking studies indicate the presence of PCDGF binding sites with a molecular weight similar to those of binding sites on CCL64 cells on the surface of two other PCDGF-responsive cell lines, 3T3 fibroblasts and PC cells. These data suggest that the receptors for PCDGF are widely distributed on cells of distinct embryonic origin.

Affinity Labels↗
PubMed1998

What amino acid properties affect protein evolution?

We studied 10 protein-coding mitochondrial genes from 19 mammalian species to evaluate the effects of 10 amino acid properties on the evolution of the genetic code, the amino acid composition of proteins, and the pattern of nonsynonymous substitutions. The 10 amino acid properties studied are the chemical composition of the side chain, two polarity measures, hydropathy, isoelectric point, volume, aromaticity, aliphaticity, hydrogenation, and hydroxythiolation. The genetic code appears to have evolved toward minimizing polarity and hydropathy but not the other seven properties. This can be explained by our finding that the presumably primitive amino acids differed much only in polarity and hydropathy, but little in the other properties. Only the chemical composition (C) and isoelectric point (IE) appear to have affected the amino acid composition of the proteins studied, that is, these proteins tend to have more amino acids with typical C and IE values, so that nonsynonymous mutations tend to result in small differences in C and IE. All properties, except for hydroxythiolation, affect the rate of nonsynonymous substitution, with the observed amino acid changes having only small differences in these properties, relative to the spectrum of all possible nonsynonymous mutations.

Amino Acid Substitution↗
PubMed1998

Regulation of mouse colony-stimulating factor-1 gene promoter activity by AP1 and cellular nucleic acid-binding protein.

Macrophage colony-stimulating factor (M-CSF; CSF-1) is a member of a complex network of cytokines that regulate monocytic cell development and activity. It is produced in nearly all organs by cell types commonly found in connective tissue, including fibroblasts and monocytes. Whether different cell types share common or have divergent mechanisms for regulating CSF-1 gene expression is not known. To address this question, the identity of cis-acting elements and cognate trans-acting factors was characterized in a region of the CSF-1 promoter known to be more active in monocytes than in fibroblasts. The results of DNase I protection assays performed with fibroblast- or monocyte-derived nuclear extracts revealed a difference in the pattern of DNA-binding proteins. One protected region, common to both fibroblasts and monocytes, spans a putative phorbol ester-responsive element (TRE), and binding to the TRE by AP1 was verified with antibodies directed against c-fos and c-jun family members. Mutational analysis revealed that the TRE is required for CSF-1 gene expression in proliferating fibroblasts and monocytes. Binding of a second putative trans-acting factor, preferentially expressed in fibroblasts, to the region immediately upstream of the TRE was also detected. Screening a mouse expression library with oligonucleotides spanning the putative cis-acting element identified cellular nucleic acid-binding protein (CNBP) as the cognate binding activity, and antiserum to CNBP disrupted the electromobility shift assay complex. Mutational analysis revealed that loss of CNBP binding leads to a decrease in CSF-1 promoter activity in fibroblasts but has no effect on CSF-1 promoter activity in monocytes. Our results demonstrate that control of CSF-1 gene expression in monocytes and fibroblasts is mediated by common and cell type-specific trans-acting factors.

Animals↗