Biomedical subjects

S Yu

Publications and source records attributed to S Yu.

At least 19 recordsLinked to original sources

PubMed2002

LC-MS/MS determination of a farnesyl transferase inhibitor in human plasma and urine.

To support clinical pharmacokinetic studies in cancer patients, sensitive and specific methods for measuring 4-[1-(4-cyanobenzyl)-5-imidazolylmethyl]-1-(3-chlorophenyl) piperazinone (I), a farnesyl transferase inhibitor (FTI), in human plasma and urine were developed and validated. The methods are based on high-performance liquid chromatography (HPLC) with atmospheric pressure chemical ionization (APCI) and tandem mass spectrometric (MS/MS) detection in the positive ion mode using a heated nebulizer interface. Drug and internal standard were isolated from plasma or basified urine using automated solid-phase extraction on cyano cartridges. The organic extracts were dried, reconstituted in aqueous acetonitrile and injected into the system. Chromatographic separation of I and internal standard (IS) was achieved using a BDS Hypersil C8 analytical column, with a mobile phase consisting of acetonitrile:methanol:water (50:4:46) and trifluoroacetic acid (0.05%) at a flow rate of 0.6 ml/min. MS/MS detection was performed on a PE-Sciex API 300 tandem mass spectrometer operated in selected reaction monitoring mode. The parent-->product ions monitored were m/z 406-->195 for analyte I and m/z 448-->195 for the internal standard. Unusual in this method is that quantitation is accomplished using a secondary product ion, m/z 195, of drug I and IS. The assays were validated over the concentration range of 0.5-1000 ng/ml (1.2 nM to 2.5 microM, respectively) in plasma, and 2.5-500 ng/ml (6.2 nM to 1.23 microM) in urine. Accuracy was within +/-10% of nominal concentration at all levels in urine, and all but the lowest standard in plasma (+/-14% at 0.5 ng/ml). Intraday precision (expressed as coefficients of variation, CVs) for standard replicates and interday precision for quality control (QC) samples were less than 8% at all concentrations in both matrices. Detailed descriptions of the extraction procedure and analytical methodology used in the assay of I in plasma and urine are presented. This procedure may have utility in the quantitation of other imidazole-based FTIs with cyanobenzyl substructures.

Alkyl and Aryl Transferases↗

PubMed2002

Ascopyrone P, a novel antibacterial derived from fungi.

AIMS: To assess the antimicrobial efficacy of ascopyrone P (APP), a secondary metabolite formed by the fungi Anthracobia melaloma, Plicaria anthracina, Plic. leiocarpa and Peziza petersi belonging to the order Pezizales. METHODS AND RESULTS: In vitro testing using a well diffusion procedure showed that APP at a high concentration (approximately 5%) inhibited the growth of Gram-positive and Gram-negative bacteria. Using an automated microbiology reader, growth curve analysis showed that 2000-4000 mg l(-1) APP caused total or significant bacterial inhibition after incubation for 24 h at 30 degrees C. Against certain yeast strains, 1000- 2000 mg l(-1) APP enhanced growth, although at higher concentrations inhibition of some yeasts was observed. Clostridium and fungal strains were not sensitive to 2000 mg l(-1) APP. No significant cidal effect was observed after 2 h against Listeria monocytogenes or Escherichia coli. Results were identical whether the APP samples tested had been produced enzymatically or chemically. CONCLUSIONS: At a level of 2000 mg l(-1), APP demonstrated growth inhibitory activity against a broad range of bacteria, but not yeasts or moulds. SIGNIFICANCE AND IMPACT OF THE STUDY: A possible application for this novel natural antimicrobial is in food preservation, to control the growth of Gram-negative and Gram-positive bacteria in raw and cooked foods. Effective dosage levels would be 500-4000 mg kg(-1), depending on food type. The efficacy, organoleptic and safety aspects of this compound in food still need to be assessed.

Anti-Bacterial Agents↗

PubMed2002

A low-selenium diet increases thyroxine and decreases 3,5,3'triiodothyronine in the plasma of kittens.

The effect of a low-selenium diet on thyroid hormone metabolism was investigated in growing kittens. Twelve specific-pathogen-free kittens with ages ranging from 16 to 18 weeks were divided into two groups of equal number with equal sex distribution in each group. One group was fed a yeast-based low-selenium diet (0.02 mg Se/kg diet) while the other group was fed the same diet supplemented with Na2SeO3 at 0.4 mg Se/kg diet for 8 weeks. Food intake, body weight and body weight gain were not affected by the low-Se diet during the study period. However, kittens given the low-Se diet had significantly reduced plasma selenium concentration and glutathione peroxidase activity. Plasma total thyroxine (T4) increased and total 3,5,3'triiodothyronine (T3) decreased significantly in kittens fed the low-Se diet at the end of the study. These results suggest that type I deiodinase in cats is a selenoprotein- or a selenium-dependent enzyme.

Animals↗

PubMed2002

Excessive hepatic copper accumulation in jaundiced rats fed a high-copper diet.

The response of copper metabolism to dietary copper challenge was investigated in jaundiced rats with elevated plasma concentrations of conjugated bilirubin as a result of impaired canicular transport of bilirubin glucuronides. Control and jaundiced rats were fed purified diets with either normal (64 micromol Cu/kg) or high (640 micromol Cu/kg) concentration of added copper. Copper loading produced a greater increase in hepatic copper concentrations in the jaundiced than in control rats. The greater dietary-copper-induced increase in hepatic copper in the jaundiced rats can be explained by the observed smaller rise in biliary copper excretion and a greater efficiency of dietary copper absorption. In individual rats, there was a positive relationship between hepatic copper concentrations and biliary copper concentrations. It is suggested that not the transport of copper from liver cells to bile but that from plasma to bile is diminished in the jaundiced rats. The elevated plasma copper concentrations in the jaundiced rats may support this suggestion.

Animal Feed↗

PubMed2002

Efficacy and safety of pioglitazone in type 2 diabetes: a randomised, placebo-controlled study in patients receiving stable insulin therapy.

The glycaemic and lipid effects of treatment with pioglitazone in combination with a stable insulin regimen were evaluated in patients with type 2 diabetes. Patients (n=566) receiving stable insulin regimens for > or = 30 days yet who had HbA1c > or = 8.0% and C-peptide > 0.7 microg/l were randomised to receive once-daily 15 mg pioglitazone, 30 mg pioglitazone, or placebo in a 16-week multicentre, double-blind, placebo-controlled trial. Per study protocol, the insulin dose was to remain unchanged, but could be decreased in response to hypoglycaemia. At the end of double-blind treatment, patients receiving pioglitazone (15 mg or 30 mg) showed statistically significant mean decreases relative to baseline HbA1c (-1.0 and -1.3, respectively; p<0.0001) and fasting plasma glucose (FPG) (-34.5 mg/dl [-1.92 mmol/l] and -48.0 mg/dl [-2.67 mmol/l], respectively; p<0.0001); these differences compared with placebo were also significant (p<0.0001). Pioglitazone (15 or 30 mg) yielded significant increases in HDL-C levels (mean increases ranging from +7.1% to + 9.3%) compared with baseline or placebo (p<0.01). The 30 mg dose also significantly reduced mean triglyceride levels (-23.7%) compared with placebo (p=0.0218). No consistent changes in TC or LDL-C levels were observed. The incidence of adverse events was similar in all treatment groups, although the incidences of weight increase, hypoglycaemia and oedema were higher among patients receiving insulin plus pioglitazone. There was no evidence of hepatotoxicity or drug-induced elevations of serum ALT > or = 3 x ULN. Pioglitazone, when added to stable insulin regimens, significantly improved HbA1c and FPG in type 2 diabetes. Pioglitazone treatment also provided significant benefit with respect to plasma HDL-C and triglyceride levels. Whether these lipid changes have an impact on overall diabetic complications remains to be determined.

Adult↗

PubMed2002

Inferior vena caval filters following deep vein thrombosis in patients with ruptured intracranial aneurysm.

Anticoagulant therapy is highly effective and prevents death in more than 95% of patients who have suffered pulmonary embolism following deep vein thrombosis. Inferior vena caval filters provide an alternative to full anticoagulation in those patients at highest risk of catastrophic haemorrhagic complications. We report on two patients who developed deep vein thrombosis following ruptured unsecured intracranial aneurysms. Inferior vena caval filters were inserted prior to aneurysm clipping, as a prophylactic measure to prevent pulmonary embolism while awaiting surgery. The patients did not receive anticoagulant therapy following successful clipping of the aneurysm. Both patients had clinical resolution of the lower limb swelling and no radiological evidence of propagation of the thrombus. During 18 months of follow-up there were no complications and no evidence of post-thrombotic syndrome.

Aneurysm, Ruptured↗

PubMed2001

Role of TGFbeta in development of spontaneous autoimmune thyroiditis in NOD.H-2h4 mice.

Nearly 100% of NOD.H-2h4 mice develop spontaneous autoimmune thyroiditis (SAT) and produce anti-mouse thyroglobulin autoantibodies when they receive 0.05% NaI in their drinking water beginning at 8 wk of age. Our previous studies showed that TGFbeta1 mRNA was constitutively expressed in thyroids and spleens of normal NOD.H-2h4 mice but not other strains of mice. To determine whether TGFbeta might have a role in SAT, mice were given anti-TGFbeta mAb at various times during development of SAT. Anti-TGFbeta markedly inhibited development of SAT and production of anti-mouse thyroglobulin IgG1 autoantibodies. Anti-TGFbeta was most effective in inhibiting SAT when given during the time thyroid lesions were developing, i.e., starting 4 wk after administration of NaI water. The active form of the TGFbeta1 protein was present in thyroids of mice with SAT but not in normal NOD.H-2h4 thyroids. However, thyrocytes of normal NOD.H-2h4 thyroids did express latent TGFbeta1. TGFbeta1 protein expression in the thyroid correlated with SAT severity scores, and administration of anti-TGFbeta inhibited TGFbeta1 protein expression in both the thyroid and spleen. TGFbeta1 was produced primarily by inflammatory cells and was primarily localized in areas of the thyroid containing clusters of CD4(+) T and B cells. Depletion of CD8(+) T cells had no effect on TGFbeta1 protein expression. Activation of splenic T cells was apparently not inhibited by anti-TGFbeta, because up-regulation of mRNA for cytokines and other T cell activation markers was similar for control and anti-TGFbeta-treated mice. TGFbeta1 may function by promoting migration to, or retention of, inflammatory cells in the thyroid.

Animals↗

PubMed2001

Sequence and structure of the mouse gene for RPE65.

PURPOSE: To determine the genomic organization of the mouse gene for the retinal pigment epithelium (RPE) specific protein RPE65. METHODS: A genomic clone containing the entire Rpe65 gene was isolated from a mouse genomic P1 library. Fragments of this clone were subcloned and sequenced by automated fluorescent dideoxy DNA sequencing and analyzed. Direct sequencing of PCR amplification products was used to complete the structure. Primer extension analysis was used to determine the transcription start site. RESULTS: Southern hybridization of restriction digests of mouse genomic DNA reveals a likely single autosomal gene for Rpe65 with no evidence of pseudogenes. Sequence analysis of the mouse P1 clone for Rpe65 and fragments thereof reveals 14 exons distributed over 27 kbp. The transcription start site is located 57 bp upstream of the initiation codon. The protein encoded by the mouse Rpe65 gene is highly conserved when compared with RPE65s from other species. CONCLUSIONS: RPE65 is a highly conserved protein and it appears that the genes for the mouse and human RPE65s, at least, are also conserved in overall structure.

Amino Acid Sequence↗

PubMed2001

Functional cloning of Src-like adapter protein-2 (SLAP-2), a novel inhibitor of antigen receptor signaling.

In an effort to identify novel therapeutic targets for autoimmunity and transplant rejection, we developed and performed a large-scale retroviral-based functional screen to select for proteins that inhibit antigen receptor-mediated activation of lymphocytes. In addition to known regulators of antigen receptor signaling, we identified a novel adaptor protein, SLAP-2 which shares 36% sequence similarity with the known Src-like adaptor protein, SLAP. Similar to SLAP, SLAP-2 is predominantly expressed in hematopoietic cells. Overexpression of SLAP-2 in B and T cell lines specifically impaired antigen receptor-mediated signaling events, including CD69 surface marker upregulation, nuclear factor of activated T cells (NFAT) promoter activation and calcium influx. Signaling induced by phorbol myristate acetate (PMA) and ionomycin was not significantly reduced, suggesting SLAP-2 functions proximally in the antigen receptor signaling cascade. The SLAP-2 protein contains an NH2-terminal myristoylation consensus sequence and SH3 and SH2 Src homology domains, but lacks a tyrosine kinase domain. In antigen receptor-stimulated cells, SLAP-2 associated with several tyrosine phosphorylated proteins, including the ubiquitin ligase Cbl. Deletion of the COOH terminus of SLAP-2 blocked function and abrogated its association with Cbl. Mutation of the putative myristoylation site of SLAP-2 compromised its inhibitory activity and impaired its localization to the membrane compartment. Our identification of the negative regulator SLAP-2 demonstrates that a retroviral-based screening strategy may be an efficient way to identify and characterize the function of key components of many signal transduction systems.

Adaptor Proteins, Signal Transducing↗

PubMed2001

A soluble dominant negative fibroblast growth factor receptor 4 isoform in human MCF-7 breast cancer cells.

Fibroblast growth factor receptors (FGFRs) are receptor tyrosine kinases encoded by four closely related genes. FGFR 1, 2, and 3 have a number of isoforms derived by alternative splicing, alternative initiation and exon switching; however, FGFR4 has been reported to encode a single intact receptor with three extracellular immunoglobulin (Ig)-like domains, a transmembrane domain, and a split intracellular kinase. Here we describe a novel C-terminally truncated soluble isoform of FGFR4 expressed by human epithelial breast cancer MCF-7 cells. This isoform results from failure of splicing of intron 4 resulting in an mRNA species that encodes an in-frame premature stop codon. Cells transfected with the corresponding cDNA containing intron 4 express a truncated releasable protein that is identified in conditioned media. This soluble FGFR4 isoform (sFGFR4) abrogates the effect of FGF-1-induced MAPK phosphorylation and PRL gene activation. These findings represent the first description of an endogenous soluble C-terminally truncated FGFR4 isoform with FGF modulatory properties.

3T3 Cells↗

PubMed2001

Human peroxisome proliferator-activated receptor alpha (PPARalpha) supports the induction of peroxisome proliferation in PPARalpha-deficient mouse liver.

Peroxisome proliferators, which function as peroxisome proliferator-activated receptor alpha (PPARalpha) agonists, induce peroxisomal, microsomal, and mitochondrial fatty acid oxidation enzymes, in conjunction with peroxisome proliferation, in liver cells. Sustained activation of PPARalpha leads to the development of liver tumors in rats and mice. The assertion that synthetic PPARalpha ligands pose negligible carcinogenic risk to humans is attributable, in part, to the failure to observe peroxisome proliferation in human hepatocytes. To explore the mechanism(s) of species-specific differences in response to PPARalpha ligands, we determined the functional competency of human PPARalpha in vivo and compared its potency with that of mouse PPARalpha. Recombinant adenovirus that expresses human or mouse PPARalpha was produced and administered intravenously to PPARalpha-deficient mice. Human as well as mouse PPARalpha fully restored the development of peroxisome proliferator-induced immediate pleiotropic responses, including peroxisome proliferation and enhanced expression of genes involved in lipid metabolism as well as nonperoxisomal genes, such as CD36, Ly-6D, Rbp7, monoglyceride lipase, pyruvate dehydrogenase kinase-4, and C3f, that have been identified recently to be up-regulated in livers with peroxisome proliferation. These studies establish that human PPARalpha is functionally competent and is equally as dose-sensitive as mouse PPARalpha in inducing peroxisome proliferation within the context of mouse liver environment and that it can heterodimerize with mouse retinoid X receptor, and this human PPARalpha-mouse retinoid X receptor chimeric heterodimer transcriptionally activates mouse PPARalpha target genes in a manner qualitatively similar to that of mouse PPARalpha.

Animals↗

PubMed2001

'In vivo perfusion Turnbull's reaction' for Fe(II) histochemistry in non-anoxic/non-ischemic and anoxic/ischemic cat brains.

We developed a simple but ingenious histochemical method, 'in vivo perfusion-Turnbull's reaction', for the visualization of non-heme Fe(II) of the brain; in situ release of Fe(2+) ions was coupled with formation of insoluble reaction product (Turnbull's blue) by in vivo perfusion of acid ferricyanide through the abdominal (non-anoxic/non-ischemic brain) or ascending (anoxic/ischemic brain) aorta in the deeply anesthetized adult cats. Frozen sections of the brain were treated according to the method of Nyguen-Legros et al. [12] to intensify Turnbull's reaction. The method revealed that cytoplasmic Fe(III) was reduced to Fe(II) in oligodendroglias in anoxic/ischemic (for 20 min) brains, and that Fe(II) was concentrated in the neuronal and glial cell nuclei regardless of the presence or absence of blood supply impairment.

Animals↗

PubMed2001

The mapping of nucleosomes and regulatory protein binding sites at the Saccharomyces cerevisiae MFA2 gene: a high resolution approach.

We have developed an end-labelling approach to map the positions of nucleosomes and protein binding sites at nucleotide resolution by footprinting micrococcal nuclease (MNase)-sensitive sites. Using this approach we determined that the MFA2 gene and its upstream control regions have four positioned nucleosomes when transcription is repressed in mating type alpha cells and that the nucleosomes lose their positioning when the gene became transcriptionally active in mating type a cells. We also detected MNase-hypersensitive sites in the alpha2 operator region of MFA2 in alpha cells but not in a cells. These probably result from the change in the local DNA conformation due to protein(s) binding in this region that governs MFA2 transcription.

Base Sequence↗

PubMed2001

Efficient asymmetric synthesis of biologically important tryptophan analogues via a palladium-mediated heteroannulation reaction.

A novel and concise synthesis of optically active tryptophan derivatives was developed via a palladium-catalyzed heteroannulation reaction of substituted o-iodoanilines with an internal alkyne. The required internal alkyne 14a or 25 was prepared in greater than 96% de via alkylation of the Schöllkopf chiral auxiliary 19 employing diphenyl phosphate as the leaving group. The Schöllkopf chiral auxiliary was chosen here for the preparation of L-tryptophans would be available from D-valine while the D-isomers required for natural product total synthesis would originate from the inexpensive L-valine (300-g scale). Applications of the palladium-catalyzed heteroannulation reaction were extended to the first asymmetric synthesis of L-isotryptophan 38 and L-benz[f]tryptophan 39. More importantly, the optically pure 6-methoxy-D-tryptophan 62 was prepared by this protocol on a large scale (>300 g). This should permit entry into many ring-A oxygenated indole alkaloids when coupled with the asymmetric Pictet-Spengler reaction. In addition, an improved total synthesis of tryprostatin A (9a) was accomplished in 43% overall yield employing this palladium-mediated process.

Alkylation↗

PubMed2001

Pharmacokinetic study of intralesional cisplatin for the treatment of hepatocellular carcinoma.

BACKGROUND: In the current study the authors examined the pharmacokinetics of direct intralesional injection of cisplatin/epinephrine/bovine collagen gel in patients with hepatocellular carcinoma and cirrhosis. METHODS: Six patients with cirrhosis and unresectable hepatocellular carcinoma received a direct intralesional injection (range, 6.7-26.7 mg) into their tumors under ultrasonographic guidance. The authors determined the total cisplatin (Pt) concentration in the plasma and urine and nonprotein-bound free Pt in plasma ultrafiltrate using flameless atomic absorption spectrometry. Data from individual patients were analyzed to calculate the pharmacokinetic parameters via a noncompartmental method for constant infusion. To demonstrate that the changes in pharmacokinetics are not related to the underlying cirrhosis, a similar methodology was applied to measure the pharmacokinetic parameters of four similar patients who were treated with cisplatin, 75 mg/m(2), as a 1-hour intravenous infusion. RESULTS: The time to attain maximum concentration of total Pt after intralesional injection was dose-dependent and ranged from 2-13 hours. The concentration-time curve was biphasic in nature. The initial half-life of total Pt in patients who received an intralesional injection varied with the cisplatin dose. The initial half-life for cisplatin doses < 15 mg was approximately 9 hours and the initial half-life at higher cisplatin doses (> 15 mg) was approximately 25 hours. The area under the curve (AUC) was dose-dependent with values ranging from 38-150 microm/mL x hour. Pharmacokinetic parameters for free Pt (ultrafiltrate) were significantly different. The time to attain maximum concentration (t-max) and terminal half-life were shorter and the average AUC was approximately 100-fold lower than total Pt. After the intravenous infusion of cisplatin, the t-max for total and free Pt was 1.3 hours and 1.1 hours, respectively. The terminal half-life and average AUC for total Pt was 194 hours and 247 microg/mL per hour, respectively, and its corresponding parameters for free Pt after intravenous infusion were much lower, similar to the findings for the intralesional injection. CONCLUSIONS: The prolonged t-max and initial half-life noted with the intralesional injection of cisplatin/epinephrine/collagen gel are consistent with its proclaimed ability to retain cisplatin at the tumor and delay its release in systemic circulation. The kinetics of intralesional cisplatin injection also suggest local sequestration of the drug in the injected site. Parameters of intravenous cisplatin infusion in cirrhotic patients are similar to those of patients from the historic control group.

Aged↗

PubMed2001

Beam propagation of x rays in a laser-produced plasma and a modified relation of interferometry in measuring the electron density.

In this paper, using a quantum mechanical technique and introducing the so-called V representation (where the representation transformation is made by using the potential Hamiltonian V), we studied x-ray propagation in a linear plasma medium both analytically and numerically. A modified relation between the phase of the probe and the reference light and the electron density of the plasma is derived, in which the contribution of the gradient of the electron density has been taken into account. It is shown that this relation has the advantage in measurements of the electron density of a plasma using the x-ray interferometry technique of lessening the errors originating from the electron density gradient. The validity of x-ray interferometry is discussed in both mathematical and physical terms.

Journal Article↗

PubMed2001

Reaction-controlled phase-transfer catalysis for propylene epoxidation to propylene oxide.

The epoxidation of olefins with H2O2 was performed with a tungsten-containing catalyst. This insoluble catalyst forms soluble active species by the action of H2O2, and when the H2O2 is used up, the catalyst precipitates for easy recycling. Thus, the advantages of both homogeneous and heterogeneous catalysts are combined in one system through reaction-controlled phase transfer of the catalyst. When coupled with the 2-ethylanthraquinone/2-ethylanthrahydroquinone redox process for H2O2 production, O2 can be used for the epoxidation of propylene to propylene oxide with 85% yield based on 2-ethylanthrahydroquinone without any co-products. This approach avoids the problematic co-products normally associated with the industrial production of propylene oxide.

Journal Article↗

PubMed2001

[Diagnosis and treatment of brain tumors in jugular foramen region].

OBJECTIVE: To analyze the diagnosis and treatment of brain tumors in jugular foramen region. METHODS: 22 patients with brain tumor in jugular foramen region who had been diagnosed and treated from 1996 to 2000. Considerable literature was reviewed. RESULTS: Tumor imaging technique showed masses of different shapes in unilateral jugular foramen region. All of the 22 patients underwent operation via different approaches. Total removal of the tumor was achieved in 20 patients and subtotal removal in 2. Pathological examination confirmed the diagnosis of neurinoma in 13 patients, tumor of glomus jugulare in 4, meningioma in 3, chordoma in 1, and metastatic tumor in 1. Only one patient died after operation. The mortality rate was as low as 4.5%. CONCLUSION: The most common tumors in jugular foramen region are neurinoma, tumor of glomus jugulare, and meningioma. Surgery is effective in treatment of brain tumor in jugular foramen region.

Adolescent↗