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Biomedical subjects

W Li

Publications and source records attributed to W Li.

At least 1,171 records · Page 65Linked to original sources
PubMed1994

Transcriptional regulation of the apoC-III gene by insulin in diabetic mice: correlation with changes in plasma triglyceride levels.

Insulin-dependent diabetes mellitus (IDDM) is associated with elevated plasma triglyceride levels that normalize after insulin administration. The observation that overexpression of the apoC-III gene in transgenic mice can cause hypertriglyceridemia and other evidence implicating apoC-III in the regulation of triglyceride levels prompted us to examine whether apoC-III might be involved in the hypertriglyceridemia associated with IDDM. To this end, the regulation of apoC-III gene expression was studied in the streptozotocin-treated mouse model of IDDM. In the insulin-deficient diabetic state, these mice have elevated glucose and triglyceride levels and a 1.4- to 1.5-fold increase in hepatic apoC-III mRNA levels, by Northern analysis as well as quantitative solution hybridization RNase protection assay. Insulin treatment normalized the glucose and triglyceride levels and diminished hepatic apoC-III mRNA levels by 59%. Analysis of transcription rates using the nuclear run-on technique demonstrated that the changes in hepatic apoC-III mRNA levels were the results of changes in the transcriptional activity of the gene. To determine the role of insulin in the regulation of apoC-III transcription, HepG2 cells were transfected with an apoC-III reporter construct, and treated with different insulin concentrations. The results demonstrated that insulin treatment induced a dose-dependent down-regulation of apoC-III transcriptional activity. These data suggest that the apoC-III transcriptional changes seen in animals are caused by differences in insulin concentrations. Assuming that apoC-III mRNA levels reflect the synthesis and secretion of the protein, these results present the possibility that overexpression of the apoC-III gene could contribute to the hypertriglyceridemia observed in IDDM.

Animals↗
PubMed1994

[Chemical studies of Epimedium acuminatum Franch].

Three flavonol glycosides isolated from the aerial parts of Epimedium acuminatum were identified as baohuoside II, epimedoside A and icariin on the basis of spectral data (UV, IR, MS, and 1HNMR) and chemical properties. Baohuoside II was isolated from the species for the first time.

Drugs, Chinese Herbal↗
PubMed1994

Effects of liuwei dihuang wan [symbol: see text:bd and some other TCM drugs on bone biomechanics and serum 25 (OH)D3 content in rats.

After a relatively long-term injection of hydrocortisone into rats, the strength of bone (anti-stress capacity) reduced evidently, while the rigidity (anti-deformity capacity) increased markedly (ie, bone fragility elevated). At the same time, the content of serum 25(OH)D3 decreased remarkably. After oral administration of Liuwei Dihuang Wan ([see symbol: see text]), anti-stress capability of bone increased evidently and its anti-deformity capability returned to normal; however, there was no elevation of serum 25(OH)D3 content. The effect of Longmu Zhuanggu Chongji ([see symbol: see text]) or Jisheng Shenqi Wan (see symbol: see text]) was lower than that of Liuwei Dihuang Wan. The experiments suggests that Liuwei Dihuang Wan is beneficial to preventing and curing osteoporosis, but no correlation between its mechanism and the metabolism of 25(OH)D3 was demonstrated.

Animals↗
PubMed1994

Detection of cytomegalovirus genome by in situ hybridization in paraffin embedded endomyocardial biopsy specimens of viral myocarditis.

Cytomegalovirus (CMV) genes were detected by in situ hybridization in 25 Chinese patients with viral myocarditis (VMC). The positive hybridization signals were found in cardiomyocytes (6 cases, 24%), capillary endothelial cells (4 cases, 16%) and interstitial cells (7 cases, 28%). The difference between VMC and control group (16 cases died of brain trauma and 10 cases of congenital heart diseases was statistically significant. There was no definite pathomorphological relationship between the detection of CMV genes and myocardial lesions. The results suggest that CMV infection may be one of the causes of myocarditis and chronic stimulation of the immune system induced by CMV may be a possible pathogenesis of this disease.

Adolescent↗
PubMed1994

[Ultrastructural change of brain ganglion of Oncomelania hupensis after immersion in sodium pentachlorophenate].

The ultrastructure of the fibrous sheath, the layer of ganglionic cell bodies and the neuropil of brain ganglion of Oncomelania hupensis was first observed under transmission electron microscope. Ultrastructural changes were found in the brain ganglion after immersing the snails in sodium pentachlorophenate. The mitochondria of nerve fibers and neurons showed denaturation and necrosis, and glycogen in neurones was markedly reduced; the neuropil also exhibited denaturation and necrosis. The ultrastructural findings may explicate in some way the mechanism of molluscicidal action of NaPcP on Oncomelania hupensis via its action on the nervous system (Figs. 1-6).

Animals↗
PubMed1994

Different responses of choriocapillary endothelial cells and retinal capillary endothelial cells to mitogenic and vasoactive factors.

The responses of choriocapillary endothelial cells (CCE) and retinal capillary endothelial cells (RCE) in culture, in terms of phosphoinositide (PI) breakdown and cellular mitogenesis, to retinal pigment epithelial cell (RPE)-conditioned medium and vasoactive agents have been compared. RPE-conditioned medium did not induce PI breakdown in either type of cell. However, it stimulated DNA synthesis in CCE but not in RCE. Bradykinin (BDK) acted as both a fast signaling and a slow mitogenic factor on CCE, but BDK did not affect PI turnover or DNA synthesis in RCE. In contrast, thrombin stimulated PI turnover in RCE but not in CCE, though it did not induce 3H-thymidine incorporation into either type of cell. These differences in cellular functions between CCE and RCE following stimulation suggest that induction of DNA synthesis and receptor-mediated PI turnover by external factors is determined, at least in part, by the origin of the capillary endothelial cell. Therefore, extrapolation to CCE pathophysiology from experiments using endothelial cells from other capillary origins may not be valid.

Animals↗
PubMed1994

[A new serotype of Salmonella III b].

A new serotype of Salmonella No. S. 3337 was isolated from the intestinal content of reptile a snake in August 1989. Providing with Salmonella biological characteristics, it could be classified into subspecies III b because it utilized sodium malonate, attacked lactose promptly, ONPG positive, and did not ferment dulcitol. H antigens appeared diphasic. Antigenic analysis shows that it represents a new serotype with an antigenic formula of 65 : z : z55.

Animals↗
PubMed1994

[A new species of Pseudomonas].

A strain No. 9191 isolated from fruit juice mineral drink is gram-negative short-rod. It differs from reported species of Pseudomonas in morphological, physiological and biochemical characteristics. Main characteristics of No. 9191 are single polar flagelled, oxidase and catalase positive, no acid from glucose but producing alkali, nitrate reduced to nitrite, inability to hydrolize gelatin and starch, arginine dihydrolase absent, no growth in presence of 0.85% NaCl. The G+C mol% of DNA is 65.15. It is named Pseudomonas halosensibilis Zou & Cai nov. sp. by the sensibility property for salt.

Beverages↗
PubMed1994

Rabbit pneumothorax. Feasibility of an animal model to simulate neonatal pneumothorax.

RATIONALE AND OBJECTIVES: The feasibility of developing an animal model to simulate radiographic features of neonatal pneumothorax was investigated, and supine computed radiography (CR) and film-screen radiography (FS) images were compared. METHODS: 5-Fr pigtail catheters were inserted into the right pleural space of three New Zealand white rabbits. Two CR and two FS supine images were obtained using identical technique. After serial 4-mL injections of air, one CR and one FS supine image were obtained. The images were masked and randomized, and four radiologists reviewed the images for typical signs of pneumothorax. Chest computed tomography (CT) was performed before the injection of any air and after completion of the study. RESULTS: At zero-mL air volume, radiologists did not perceive a pneumothorax. As the air volume increased, the number of signs of a pneumothorax increased; there was no significant difference between CR and FS in the number of signs of pneumothorax detected at any volume. Chest CT confirmed that there was no unexplained air leak. The volume of air injected correlated with the calculated volume from the CT. CONCLUSIONS: This induced, volume-controlled, animal model simulated the supine radiographic features of neonatal pneumothorax.

Animals↗
PubMed1994

Nutritional status of preschool children in poor rural areas of China.

Described are the main findings of the first large-scale nutrition monitoring project carried out over a 4-year period in China. The nutritional status of nearly 10,000 preschool children in 18 comparatively poor rural areas in seven provinces was followed each year over the period 1986-89 in order to identify their major nutritional problems and improve their growth and development. Physical measurements were made and dietary surveys and biochemical tests were performed on a subsample of the children. The proportion of stunted and underweight children was far higher than the national average. Based on the possibilities offered by local circumstances, the prevalences of stunting and underweight were lowered and anaemia was greatly reduced. Along with the progress in nutrition monitoring, major efforts were made to train health workers, as well as to encourage increased production of green vegetables, poultry, and small livestock. The wealth of information collected and the experience gained may serve as a baseline record, the project currently being expanded to cover 100 counties throughout China.

Anemia↗
PubMed1993

Tb(III) and Eu(III) as fluorescent probes to investigate the metal-binding sites of trichosanthin.

Tb(III) and Eu(III) ions were used as fluorescent probes in the study of the trichosanthin (TCS). The fluorescence of Tb(III) was increased considerably when bound to TCS to replace the Ca(II) ions. The nonradiative energy transfer from fluorescent tryptophan (Trp) residues to the bound Tb(III) or Eu(III) took place. From a Foster d-d nonradiative energy transfer mechanism, it was obtained that the average distance between the bound Tb(III) and the Trp residue is 1.27nm. The results indicate that the major groups in TCS bound to Ca(II) ions should be the carboxylic side groups of the glutamic acid and/or aspartic acid. The fluorescent quenching of Ca(II)-free TCS by adding Tb(III) or Eu(III) into TCS from which the Ca(II) ions had been removed was discussed as well.

Binding Sites↗
PubMed1993

Effects of histone acetylation, ubiquitination and variants on nucleosome stability.

The properties of the nucleosomes of a salt-soluble, transcriptionally active gene-enriched fraction of chicken erythrocyte chromatin were evaluated by hydroxyapatite dissociation chromatography. We have demonstrated previously that the salt-soluble, transcriptionally active gene-enriched polynucleosomes are enriched in dynamically acetylated and ubiquitinated histones, and in an atypical U-shaped nucleosome that possessed about 20% less protein than a typical nucleosome. Further, newly synthesized histones H2A and H2B exchange preferentially with the nucleosomal histones H2A and H2B of this salt-soluble chromatin fraction. Analysis of the histones eluting from the hydroxyapatite-bound chromatin demonstrated that hyperacetylated and ubiquitinated (u), including multi-ubiquitinated, H2A-H2B.1 dimers dissociated at lower concentrations of NaCl than unmodified dimers or dimers with histone variants H2A.Z and/or H2B.2. Cross-linking studies revealed that at least 50% of uH2B.1 was paired with uH2A. uH2A-uH2B.1 dimers dissociated at lower NaCl concentrations than H2A-uH2B.1 dimers. Hyperacetylated histone (H3-H4)2 tetramers also eluted at lower concentrations of NaCl than unmodified tetramers. Our results support the idea that acetylation and ubiquitination of histones H2A and H2B.1 increase the lability of H2A-H2B.1 dimers in transcriptionally active nucleosomes. In contrast, our observations suggest that histone variants H2A.Z and H2B.2. stabilize the association of the H2A-H2B dimer in nucleosomes. The elevated lability of the H2A-H2B dimer may facilitate processes such as the exchange of these dimers with newly synthesized histones, the elongation process of transcription and transcription factor binding.

Acetylation↗
PubMed1993

Nck associates with the SH2 domain-docking protein IRS-1 in insulin-stimulated cells.

Nck, an oncogenic protein composed of one SH2 and three SH3 domains, is a common target for various cell surface receptors. Nck is thought to function as an adaptor protein to couple cell surface receptors to downstream effector molecules that regulate cellular responses induced by receptor activation. In this report, we show that Nck forms a stable complex in vivo with IRS-1 in insulin-stimulated cells. The interaction between IRS-1 and Nck is mediated by the binding of the SH2 domain of Nck to tyrosine-phosphorylated IRS-1. Although Nck associates with IRS-1, Nck phosphorylation is not affected by insulin stimulation. Furthermore, in vitro and in vivo studies show that the SH2 domains of Nck, GRB2, and p85 bind distinct phosphotyrosine residues in IRS-1. After insulin stimulation all three signaling molecules can be found complexed to a single IRS-1 molecule. These findings provide further evidence that, in response to insulin stimulation, IRS-1 acts as an SH2 docking protein that coordinates the regulation of various different signaling pathways activated by the insulin receptor.

Adaptor Proteins, Signal Transducing↗
PubMed1993

Tumor necrosis factor-induced activation and increased tyrosine phosphorylation of mitogen-activated protein (MAP) kinase in human fibroblasts.

Tumor necrosis factor (TNF) is a pleiotropic cytokine whose many demonstrated actions include effects on cell growth and differentiation. TNF treatment of cells is known to lead to a rapid increase in serine/threonine phosphorylation of many cellular proteins, but the kinases responsible remain largely unidentified. We show that TNF treatment induces a rapid and transient increase in mitogen-activated protein kinase (MAPK) activity in the human diploid FS-4 cell line, for which TNF is known to be mitogenic. TNF-induced activation of MAPK was demonstrated by its enhanced ability to phosphorylate myelin basic protein in vitro and by a characteristic shift in the electrophoretic mobility of MAPK proteins. MAPK activation was accompanied by a significant increase of MAPK phosphorylation on tyrosine residues, which was demonstrated by 32P labeling of cells and isolation of the labeled proteins after immunoprecipitation with antibodies to phosphotyrosine, and by direct immunoblotting of SDS-polyacrylamide gel electrophoresis-fractionated unlabeled cell lysates with antibodies to phosphotyrosine. The pp42 and pp44 MAPK were the only proteins whose tyrosine phosphorylation was demonstrably increased in FS-4 cells after TNF treatment. MAPK activation is likely to represent an important component in the cascade of signals that link TNF receptors to various TNF-elicited cellular responses.

Blotting, Western↗
PubMed1993

Specific interaction of the cyclophilin-cyclosporin complex with the B subunit of calcineurin.

Calcineurin (CaN), a Ca2+/calmodulin-dependent serine/threonine phosphatase, has been shown to be inhibited by the complex of the immunosuppressant cyclosporin A (CsA) and its receptor, cyclophilin (CyP), but not by either alone. In the current study, the topological relationship between cyclophilin and the subunits of CaN has been explored using chemical cross-linking agents. In the presence of cyclosporin, 125I-CyP, shown to bind to CsA, is extensively cross-linked to the B subunit of CaN but not the catalytic A subunit. However, the A subunit is required for binding of the CyP.CsA complex, since cross-linking to recombinant B subunit alone does not occur. The kinetics of association indicate a saturable reaction with a Kd of less than 70 nM. Cross-linking to the B subunit occurs with cross-linkers that span from 0 to 16 A and employ different cross-linking chemistry, indicating direct contact between the B subunit and CyP. Similar cross-linking to the B subunit has been observed with the complex of 125I-labeled FK506 binding protein (FKBP) and FK506 but not with the FKBP-rapamycin complex. CyP.CsA cross-linking to CaN is Ca2+/calmodulin-dependent with intact CaN, but Ca2+/calmodulin-independent after digestion to remove the calmodulin binding and autoinhibitory domain.

Amino Acid Isomerases↗
PubMed1993

Cyclophilin-40, a protein with homology to the P59 component of the steroid receptor complex. Cloning of the cDNA and further characterization.

We have reported previously the isolation and preliminary characterization of a 40-kDa cyclosporin A (CsA)-binding protein, cyclophilin-40 (CyP-40). To determine the sequence of this protein, degenerate oligonucleotide primers based on bovine brain CyP-40 tryptic peptides were used to generate a polymerase chain reaction fragment of CyP-40 cDNA. This was used to isolate the complete cDNA from a human pancreatic islet cell library. Northern analysis indicated ubiquitous distribution of CyP-40 mRNA throughout human tissues. The CyP-18 domain of CyP-40 is most similar to maize CyP (64.3% identity), whereas 150 amino acids of the non-CyP-18 domain of CyP-40 share 30.7% identity with P59, a member of the steroid receptor complex. Failure to detect glycosylation and mass spectroscopy with isolated CyP-40 indicate minimal, if any, posttranslational modification. Employing a new assay for calcineurin protein phosphatase activity to compare the effects of CyP-40.CsA and CyP-18.CsA complexes, IC50 values of 320 nM +/- 20 and 195 nM +/- 15, respectively, were obtained. A chemical cross-linking study revealed that CyP-40 competes for 125I-CyP-18 binding to calcineurin in the presence of CsA. The homology of CyP-40 to P59 suggests that CyP-40 might be involved in modulating the activity of biologically important receptors.

Amino Acid Isomerases↗