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Biomedical subjects

X Fang

Publications and source records attributed to X Fang.

At least 55 records · Page 3Linked to original sources
PubMed2001

beta-Oxidation of simvastatin in mouse liver preparations.

All current 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors [simvastatin (SV), lovastatin (LV), atorvastatin, pravastatin, fluvastatin, and cerivastatin] are believed to undergo an atypical beta-oxidation of the dihydroxy heptanoic or heptanoic acid side chain. Metabolites, which are shortened by two- and/or four-carbon units consistent with beta-oxidation products, have been reported exclusively in rodents following LV and SV administration and across species (rodents, dogs, and humans) following the other statins. In this study, in vitro formation of a beta-oxidation product of simvastatin hydroxy acid (SVA) and its intermediates in mouse livers is described. Incubation of SVA with mouse liver preparations fortified with CoASH and ATP led to formation of SV and two major products (P1 and P2). Based on mass spectrometry (MS), tandem mass spectrometry, and/or NMR spectral characteristics, P1 was an alpha,beta-unsaturated metabolite, formed by dehydration of the D,D-dihydroxy heptanoic acid side chain, whereas P2 was probably the L,D-dihydroxy acid isomer of SVA, formed by stereospecific hydration of P1. When NAD(+) was also included in the incubation mixture, there were two additional metabolites with the MS and/or NMR characteristics consistent with a two-carbon shortened product (P3) and its dehydrated derivative (P4). In a complete incubation system with all cofactors (ATP, CoASH, NAD(+), and NADPH) present, there was an additional product with MS spectra and liquid chromatography retention time identical to the beta-oxidized, unsubstituted pentanoic acid metabolite (P5) detected in rats and mice following simvastatin administration. The involvement of CoASH and NAD(+) and the presence of the four metabolic intermediates suggest that SVA (and presumably the other statins) is a substrate for the beta-oxidation enzyme complex in mice. Additionally, the present finding of CoASH-dependent formation of SV substantiates a mechanism proposed previously for the in vivo lactonization of statin hydroxy acids.

Animals↗
PubMed2001

[Clinical characteristics and diagnosis of chronic intestinal pseudo-obstruction].

OBJECTIVE: To analyze and determine the clinical characteristics and diagnostic methods of chronic intestinal pseudo-obstruction(CIP). METHODS: We reviewed the medical records of all 23 patients who diagnosed with CIP in Peking Union Medical College Hospital from 1978 to 2000. RESULTS: Twenty three patients fulfilled the diagnostic criteria (9 male, 14 female, median age 50 years, range 4-75 years). The main symptoms at the presentation were abdominal distension(87%), pain(57%), diarrhea(65%), constipation(48%), vomiting(39%) and weight loss(83%). In this group of CIP patients, the abdominal distension was more common and serious than pain, presenting with diarrhea, weight loss and dismotility in esophagus and stomach. Bowel loops and visible peristaltic waves were seldom observed in the CIP patients. The plain film showed the multiple air-fluid levels (17/20, 85%) and generalized intestinal distention and air in colon. The abnormal findings on the barium contrast examination included intestinal dilation (19/23, 83%), weaken peristalses or/and prolongation of transit time (74%) without mechanical lesions. The pseudo-obstruction involved the small intestine (83%) and colon (39%) that determined according to the radiographic features, abnormal gastrointestinal motor functions, findings of endoscopic examination and laparotomy. Eighteen cases were chronic idiopathic intestinal pseudo-obstruction (1 familial myopathy), 5 were secondary to CTD. CONCLUSIONS: Comparison with the typical mechanical obstruction, the presentations of CIP have some relatively characteristics. The clinical diagnosis of CIP can be confirmed on the basis of typical clinical symptoms and radiographic features, abnormal gastrointestinal motility.

Adolescent↗
PubMed2001

[Influence of focal adhesion kinase (FAK) on the biological behaviors of human hepatocellular carcinoma cells].

OBJECTIVE: To study the effect of reducing FAK expression on the malignant biological behaviors of FAK-overexpressed hepatocellular carcinoma cell line SMMC-7721. METHODS: FAK expression of different hepatocelluar carcinoma cell lines was detected by Western blot analysis. Antisense plasmid of FAK was constructed and transfected into SMMC-7721. RESULTS: SMMC-7721 expressed much more FAK than did hepatocyte line L02. When transfected with autisense FAK, it showed reduced growth rate and colony formation in soft agar, and the number of cells in S phase was reduced by 15%. The adhesion ability of antisense FAK-transfeected cells was also decreased with no change of integrin expression. CONCLUSION: FAK is overexpressed in the human hepatocellular carcinoma cell line SMMC-7721. Reducing the FAK expression can partly reverse the malignant behaviors of the cell line.

Blotting, Western↗
PubMed2001

[Investigation on an outbreak of Legionnaires' disease caused by Lboz in a suburb of Beijing].

OBJECTIVE: To demonstrate the infectious rates and incidence rates through epidemiological investigation. METHODS: Serum samples from 203 new soldiers were detected from Lboz by TAT. RESULTS: Infectious rates was 33.00% (67/203), and the incidence rates was 8.87% (18/203) with 2 cases of pneumonic type and 16 cases of pontiac fever type. CONCLUSION: The results suggested that an outbreak of Legionnaires' desease caused by Legionella bozemanii (Lboz) took place in a suburb of Beijing. However the report of the outbreak caused by Lboz had not been found in related references.

China↗
PubMed2001

[A new interpretation for "Knockout Drops" (menghan)].

Knockout drops ("menghanyao" in Chinese) is named as one of riddles in the cultural history of China. Why its is named as "menghan" has been interpreted from the viewpoint of phonology by many former solons. A new opinion is put forward from the viewpoint of pharmacology and physiology in this paper, in which a historical fact is concerned that mandala is the essential component in knockout drug. The function of sweat gland is inhibited with sweat retained inside the human body after knockout drops are taken. "Menghan" just describes the above physiological phenomenon.

China↗
PubMed2001

[The detection of phenol degrading strain in environment with specific primer of phenol hydroxylase gene].

A 684 bp oligonucleotide fragment was produced by PCR amplification from phenol-degrading strain Acinetobacter calcoaceticus PHEA-2 with the specific primers of gene encoding phenol hydroxylase. The nucleotide sequence of this fragment and its deduced amino acid sequence share 84% and 98% homology with the phenol hydroxylase gene and its deduced amino acid sequences of phenol-degrading strain Acinetobacter calcoaceticus NCIB8250. Sets of different aromatic compounds degrading strains were used to test this specific prime. The 684 bp-fragments were amplified only from phenol-degrading strains by PCR. When using this pair of primers to detect the bacterial isolates from wastewater discharged from coking plant, all the tested strains, which possess 684 bp characteristic fragment, showed the ability to degrade phenol in this study.

Acinetobacter calcoaceticus↗
PubMed2000

Inhibition of growth-factor-induced phosphorylation and activation of protein kinase B/Akt by atypical protein kinase C in breast cancer cells.

The protein kinase B/Akt serine/threonine kinase, located downstream of phosphoinositide 3-kinase (PI-3K), is a major regulator of cellular survival and proliferation. Atypical protein kinase C (aPKC) family members are activated by PI-3K and also contribute to cell proliferation, suggesting that Akt and aPKC might interact to activate signalling through the PI-3K cascade. Here we demonstrate that blocking PKC activity in MDA-MB-468 breast cancer cells increased the phosphorylation and activity of Akt. Functional PI-3K was required for the PKC inhibitors to increase Akt phosphorylation and activation, potentially owing to the activation of specific PKC isoforms by PI-3K. The concentration dependence of the action of the PKC inhibitors implicates aPKC in the inhibition of Akt phosphorylation and activity. In support of a role for aPKC in the regulation of Akt, Akt and PKCzeta or PKClambda/iota were readily co-precipitated from the BT-549 breast cancer cell line. Furthermore, the overexpression of PKCzeta inhibited growth-factor-induced increases in Akt phosphorylation and activity. Thus PKCzeta associates physically with Akt and decreases Akt phosphorylation and enzyme activity. The effects of PKC on Akt were transmitted through the PI-3K cascade as indicated by changes in p70 s6 kinase (p70(s6k)) phosphorylation. Thus PKCzeta, and potentially other PKC isoenzymes, regulate growth-factor-mediated Akt phosphorylation and activation, which is consistent with a generalized role for PKCzeta in limiting growth factor signalling through the PI-3K/Akt pathway.

Breast Neoplasms↗
PubMed2000

Role of IKKgamma/nemo in assembly of the Ikappa B kinase complex.

IKKgamma/NEMO is a protein that is critical for the assembly of the high molecular weight IkappaB kinase (IKK) complex. To investigate the role of IKKgamma/NEMO in the assembly of the IKK complex, we conducted a series of experiments in which the chromatographic distribution of extracts prepared from cells transiently expressing epitope-tagged IKKgamma/NEMO and the IKKs were examined. When expressed alone following transfection, IKKalpha and IKKbeta were present in low molecular weight complexes migrating between 200 and 400 kDa. However, when coexpressed with IKKgamma/NEMO, both IKKalpha and IKKbeta migrated at approximately 600 kDa which was similar to the previously described IKK complex that is activated by cytokines such as tumor necrosis factor-alpha. When either IKKalpha or IKKbeta was expressed alone with IKKgamma/NEMO, IKKbeta but not IKKalpha migrated in the higher molecular weight IKK complex. Constitutively active or inactive forms of IKKbeta were both incorporated into the high molecular weight IKK complex in the presence of IKKgamma/NEMO. The amino-terminal region of IKKgamma/NEMO, which interacts directly with IKKbeta, was required for formation of the high molecular weight IKK complex and for stimulation of IKKbeta kinase activity. These results suggest that recruitment of the IKKs into a high molecular complex by IKKgamma/NEMO is a crucial step involved in IKK function.

Animals↗
PubMed2000

Lysophosphatidic acid prevents apoptosis in fibroblasts via G(i)-protein-mediated activation of mitogen-activated protein kinase.

Lysophosphatidic acid (LPA) is a naturally occurring phospholipid with multiple biological functions. In the present study, we demonstrate that, besides its mitogenic activity, LPA is a potent survival factor, preventing serum-deprivation-induced apoptosis in fibroblasts and other cell types. Both the proliferative effect and survival activity of LPA are sensitive to the action of pertussis toxin (PTX), indicating that both processes are mediated by G(i) protein(s). We therefore focused on the role of G(i)-protein-mediated signalling events in the promotion of cell survival by LPA. In addition to activation of mitogen-activated protein kinase (MAPK), LPA stimulates a modest PTX-sensitive phosphorylation/activation of the serine/threonine kinase Akt, a survival mediator downstream of phosphoinositide 3-kinase (PI3K). Inhibition of PI3K with LY 294002 or wortmannin resulted in a marked inhibition of LPA-induced DNA synthesis, and yet the survival activity of LPA decreased by only 20-30%, suggesting a limited input of the PI3K-Akt cascade in LPA-induced cell survival. In contrast, inhibition of MAPK activation by the MEK-1 inhibitor, PD 98059, blocked both the proliferative and survival effects of LPA. These results indicate that LPA promotes cell survival largely via G(i)-protein-mediated activation of ERK1/ERK2, or other PD 98059-sensitive member(s) of the MAPK family.

3T3 Cells↗
PubMed2000

Phosphorylation and inactivation of glycogen synthase kinase 3 by protein kinase A.

Glycogen synthase kinase 3 (GSK-3) is implicated in multiple biological processes including metabolism, gene expression, cell fate determination, proliferation, and survival. GSK-3 activity is inhibited through phosphorylation of serine 21 in GSK-3 alpha and serine 9 in GSK-3 beta. These serine residues of GSK-3 have been previously identified as targets of protein kinase B (PKB/Akt), a serine/threonine kinase located downstream of phosphatidylinositol 3-kinase. Here, we show that serine 21 in GSK-3 alpha and serine 9 in GSK-3 beta are also physiological substrates of cAMP-dependent protein kinase A. Protein kinase A physically associates with, phosphorylates, and inactivates both isoforms of GSK-3. The results indicate that depending on the stimulatory context, the activity of GSK-3 can be modulated either by growth factors that work through the phosphatidylinositol 3-kinase-protein kinase B cascade or by hormonal stimulation of G protein-coupled receptors that link to changes in intracellular cAMP levels.

Animals↗
PubMed2000

Nitrosothiol esters of diclofenac: synthesis and pharmacological characterization as gastrointestinal-sparing prodrugs.

Despite its widespread use, diclofenac has gastrointestinal liabilities common to nonsteroidal antiinflammatory drugs (NSAIDs) that might be reduced by concomitant administration of a gastrointestinal cytoprotectant such as nitric oxide (NO). A series of novel diclofenac esters containing a nitrosothiol (-S-NO) moiety as a NO donor functionality has been synthesized and evaluated in vivo for bioavailability, pharmacological activity, and gastric irritation. All S-NO-diclofenac derivatives acted as orally bioavailable prodrugs, producing significant levels of diclofenac in plasma within 15 min after oral administration to mice. At equimolar oral doses, S-NO-diclofenac derivatives (20a-21b) displayed rat antiinflammatory and analgesic activities comparable to those of diclofenac in the carrageenan-induced paw edema test and the mouse phenylbenzoquinone-induced writhing test, respectively. All tested S-NO-diclofenac derivatives (20a-21b) were gastric-sparing in that they elicited markedly fewer stomach lesions as compared to the stomach lesions caused by a high equimolar dose of diclofenac in the rat. Nitrosothiol esters of diclofenac comprise a novel class of NO-donating compounds having therapeutic potential as nonsteroidal antiinflammatory agents with an enhanced gastric safety profile.

Animals↗
PubMed2000

Xarvcf, Xenopus member of the p120 catenin subfamily associating with cadherin juxtamembrane region.

The catenin ARVCF is a member of the p120(ctn) subfamily of Armadillo proteins. A number of catenins directly bind cadherin cytoplasmic tails, contributing to the modulation of cell-cell adhesion and motility processes. Some catenins, such as beta-catenin (and likely p120(ctn)), have additional roles within signaling pathways regulating gene transcription. We have isolated the Xenopus homolog of human ARVCF. Utilizing the cadherin membrane proximal region known to bind p120(ctn) and delta-catenin, coimmunoprecipitation experiments demonstrate that Xarvcf, likewise, binds cadherin in this region and that corresponding point mutations within conserved residues abrogate the Xarvcf-cadherin association. Western blot analysis of Xarvcf protein across a series of developmental stages reveals changes in protein mobility, likely due to changes in phosphorylation. Xarvcf is a maternally provided transcript and expressed in the embryo throughout all stages of development. Interestingly, Xarvcf mRNA is differentially spliced to produce several isoforms, one of which is developmentally regulated. In common with the putative post-translational modifications of the Xarvcf protein, the presence of alternative splice isoforms suggests that Xarvcf possesses the capacity to effect developmental functions in a regulatable manner.

Alternative Splicing↗
PubMed2000

Mg2+-dependent compaction and folding of yeast tRNAPhe and the catalytic domain of the B. subtilis RNase P RNA determined by small-angle X-ray scattering.

We apply synchrotron-based small-angle X-ray scattering to investigate the relationship between compaction, metal binding, and structure formation of two RNAs at 37 degrees C: the 76 nucleotide yeast tRNA(Phe) and the 255 nucleotide catalytic domain of the Bacillus subtilis RNase P RNA. For both RNAs, this method provides direct evidence for the population of a distinct folding intermediate. The relative compaction between the intermediate and the native state does not correlate with the size of the RNA but does correlate well with the amount of surface burial as quantified previously by the urea-dependent m-value. The total compaction process can be described in two major stages. Starting from a completely unfolded state (4-8 M urea, no Mg(2+)), the major amount of compaction occurs upon the dilution of the denaturant and the addition of micromolar amounts of Mg(2+) to form the intermediate. The native state forms in a single transition from the intermediate state upon cooperative binding of three to four Mg(2+) ions. The characterization of this intermediate by small-angle X-ray scattering lends strong support for the cooperative Mg(2+)-binding model to describe the stability of a tertiary RNA.

Bacillus subtilis↗
PubMed2000

Using molecular beacons to probe molecular interactions between lactate dehydrogenase and single-stranded DNA.

The interactions between two key macromolecular species, nucleic acids and proteins, control many important biological processes. There have been limited effective methodologies to study these interactions in real time. In this work, we have applied a newly developed molecular beacon (MB) DNA probe for the analysis of an enzyme, lactate dehydrogenase (LDH), and for the investigation of its properties of binding with single-stranded DNA. Molecular beacons are single-stranded oligonucleotide probes designed to report the presence of specific complementary nucleic acids by fluorescence detection. The interaction between LDH and MB has resulted in a significant fluorescence signal enhancement, which is used for the elucidation of MB/LDH binding properties. The processes of binding between MB and different isoenzymes of LDH have been studied. The results show that the stoichiometry of LDH-5/MB binding is 1:1, and the binding constant is 1.9 x 10(-7) M(-1). We have also studied salt effects, binding sites, temperature effects, pH effects, and the binding specificities for different isoenzymes. Our results demonstrate that MB can be effectively used for sensitive protein quantitation and for efficient protein-DNA interaction studies. MB has a signal transduction mechanism built within the molecule and can thus be used for the development of rapid protein assays and for real-time measurements.

DNA, Single-Stranded↗
PubMed2000

Molecular beacons: a novel DNA probe for nucleic acid and protein studies.

A new concept has been introduced for molecular beacon DNA molecules. Molecular beacons are a new class of oligonucleotides that can report the presence of specific nucleic acids in both homogeneous solutions and at the liquid-solid interface. They emit an intense fluorescent signal only when hybridized to their target DNA or RNA molecules. Biotinylated molecular beacons have been designed and used for the development of ultrasensitive DNA sensors and for DNA molecular interaction studies at a solid-liquid interface. Molecular beacons have also been used to study protein-DNA interactions. They have provided a variety of exciting opportunities in DNA/RNA/protein studies.

Animals↗