Biomedical subjects

X Chen

Publications and source records attributed to X Chen.

At least 667 records · Page 37Linked to original sources

PubMed1999

Simultaneous determination of deoxyribonucleoside in the presence of ribonucleoside triphosphates in human carcinoma cells by high-performance liquid chromatography.

Simultaneous determination of ribonucleoside and deoxyribonucleoside triphosphates in cells by HPLC is an analytical challenge since the concentration of dNTP present in mammalian cells is several orders of magnitude lower than the corresponding NTP. Hence, the quantitation of dNTP in cells is generally performed after selective oxidation or removal of the major NTP. The procedures reported so far are lengthy and cumbersome and do not enable the simultaneous determination of NTP. We report the development of a simple, direct HPLC method for the simultaneous determination of dNTP and NTP in colon carcinoma WiDr cell extracts using a stepwise gradient elution ion-pairing HPLC with uv detection at 260 nm and with a minimal chemical manipulation of cells. Exponentially growing WiDr cells were harvested by centrifugation, rinsed with phosphate-buffered saline, and carefully counted. The pellets were suspended in a known volume of ice-cold water and deproteinized with an equal volume of 6% trichloroacetic acid. The acid cell extracts (corresponding to 2. 5 x 10(6) cells/100 microl) were centrifuged at 13,000g for 10 min at 4 degrees C. The resulting supernatants were stored at -80 degrees C prior to analysis. Aliquots (100 microl) were neutralized with 4.3 microl saturated Na2CO3 solution prior the injection of 40 microl onto the HPLC column (injection speed 250 microl/min). Chromatographic separations were performed using two Symmetry C18 3. 5-microm (2 x 3.9 x 150 mm) columns (Waters), connected in series equipped with a Sentry guard column (3.9 x 20 mm i.d.) filled with the same packing material. The HPLC columns were kept at 30 degrees C. The mobile phase was delivered at a flow rate of 0.5 ml/min, with the following stepwise gradient elution program: % solvent A/solvent B, 100/0 at 0 min --> 100/0 at 1 min --> 36/64 at 5 min --> 31/69 at 90 min --> 31/69 at 105 min --> 0/100 at 106 min --> 0/100 at 120 min; 50/50 MeOH/solvent B from 121 to 130 min; 100% solvent A from 131 to 160 min. Solvent A contained 0.01 M KH2PO4, 0.01 M tetrabutylammonium chloride, and 0.25% MeOH and was adjusted to pH 7. 0 (550 microl 10 N NaOH for 1 liter solvent A). Solvent B consisted of 0.1 M KH2PO4, 0.028 M tetrabutylammonium chloride, and 30% MeOH and was neutralized to pH 7.0 (1.4 ml 10 N NaOH for 1 liter solvent B). Even though dNTPs are minor components of cell extracts, satisfactory regression coefficients were obtained for their calibration curves (r2 > 0.99) established with the addition-calibration methods up to 120 pmol/40-microl injection. The applicability of the method was demonstrated by in vitro studies of the modulation of NTP and dNTP pools in WiDr colon carcinoma cell lines exposed to various pharmacological concentrations of cytostatic drugs (i.e., FMdC, IUdR, gemcitabine). In conclusion, this optimized, simplified, analytical method enables the simultaneous quantitation of NTP and dNTP and may represent a valuable tool for the detection of minute alterations of cellular dNTP/NTP pools induced by anticancer/antiviral drugs and diseases.

Chromatography, High Pressure Liquid↗

PubMed1999

Thermophoretic Velocity of a Small Nonevaporating or Evaporating Particle in a High-Temperature Diatomic Gas.

Kinetic-theory analytical results concerning the thermophoretic velocity of a spherical nonevaporating or evaporating particle suspended in a high-temperature diatomic gas with appreciable dissociation degree (e.g., for oxygen with temperatures greater than 3000 K or for nitrogen with temperatures greater than 5500 K) are presented for the free-molecule regime. Molecular dissociation in the bulk gas and atomic recombination at the surface of the cold particle are included in the analysis. It is shown that the thermophoretic velocity of the suspended particle is directly proportional to the temperature gradient and approximately inversely proportional to the gas pressure. The thermophoretic velocities of both nonevaporating and evaporating particles are independent of the particle radius and increase slightly with increase in the specular-reflection fraction. For a nonevaporating particle, the thermophoretic velocity almost does not depend on the recombination fraction of atoms at the particle surface. For an intensely evaporating particle, the thermophoretic velocity (UTV) increases with increasing thermal accommodation factor (a) and decreases with increasing atomic recombination fraction (alpha) at high gas temperatures with appreciable molecular dissociation, while UTV almost does not depend on a and alpha at low gas temperatures. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Selection of HIV-specific immunogenic epitopes by screening random peptide libraries with HIV-1-positive sera.

Efforts to develop a protective HIV-1 vaccine have been hindered by difficulties in identifying epitopes capable of inducing broad neutralizing Ab responses. In fact, the high mutation rate occurring in HIV-1 envelope proteins and the complex structure of gp120 as an oligomer associated with gp41 result in a high degree of antigenic polymorphism. To overcome these obstacles, we screened random peptide libraries using sera from HIV-infected subjects to identify antigenic and immunogenic mimics of HIV-1 epitopes. After extensive counterscreening with HIV-negative sera, we isolated peptides specifically recognized by Abs from HIV-1-infected individuals. These peptides behaved as antigenic mimics of linear or conformational HIV-1 epitopes generated in vivo in infected subjects. Consistent with these findings, sera of simian HIV-infected monkeys also recognized the HIV-specific epitopes. The selected peptides were immunogenic in mice, where they elicited HIV-specific Abs that effectively neutralized HIV-1 isolates. These results demonstrate that pools of HIV-1 mimotopes can be selected from combinatorial peptide libraries by taking advantage of the HIV-specific Ab repertoire induced by the natural infection.

Animals↗

PubMed1999

Protein kinase C modulates aryl hydrocarbon receptor nuclear translocator protein-mediated transactivation potential in a dimer context.

Protein kinase C (PKC)- and protein kinase A (PKA)-mediated modulation of the transactivation potential of human aryl hydrocarbon receptor nuclear translocator (hARNT), a basic helix-loop-helix (bHLH)-PAS transcription factor, and the bHLH-ZIP transcription factors USF-1 (for upstream regulatory factor 1) and c-Myc were examined. An 81 nM dose of the PKC activator phorbol-12-myristate-13-acetate (PMA), shown here to specifically activate PKC in COS-1 cells, or a 1 nM dose of the PKA activator 8-bromoadenosine-3',5'-cyclic monophosphate (8-Br-cAMP) results in 2. 6- and 1.9-fold enhancements, respectively, in hARNT-mediated transactivation of the class B, E-box-driven reporter pMyc3E1bLuc relative to identically transfected, carrier solvent-treated COS-1 cells. In contrast, 81 nM PMA and 1 nM 8-Br-cAMP did not enhance transactivation of pMyc3E1bLuc-driven by USF-1 and c-Myc expression relative to identically transfected, carrier-treated COS-1 cells. Co-transfection of pcDNA3/ARNT-474-Flag, expressing a hARNT carboxyl-terminal transactivation domain deletion, and pMyc3E1bLuc does not result in induction of reporter activity, suggesting PMA's effects do not involve formation of unknown hARNT-protein heterodimers. Additionally, PMA had no effect on hARNT expression relative to Me2SO-treated cells. Metabolic 32P labeling of hARNT in cells treated with carrier solvent or 81 nM PMA demonstrates that PMA does not increase the overall phosphorylation level of hARNT. These results demonstrate, for the first time, that the transactivation potential of ARNT in a dimer context can be specifically modulated by PKC or PKA stimulation and that the bHLH-PAS and bHLH-ZIP transcription factors are differentially regulated by these pathways in COS-1 cells.

Animals↗

PubMed1999

Active sites of diacylglycerol kinase from Escherichia coli are shared between subunits.

We show that residues from different subunits participate in forming the active site of the trimeric membrane protein diacylglycerol kinase (DGK) from Escherichia coli. Five likely active-site mutants were identified: A14Q, N72S, E76L, K94L, and D95N. All five of these mutants possessed significantly impaired catalytic function, without evidence of gross structural alterations as judged by their similar near-UV and far-UV circular dichroism spectra. We found that mixtures of either A14Q or E76L with N72S or K94L possessed much greater activity than the mutant proteins by themselves, suggesting that Ala14 and Glu76 may be on one half-site while Asn72 and Lys94 are on another half-site. Consistent with the shared site model, we also found that (1) peak activity of A14Q and N72S subunit mixtures occur at equimolar concentrations; (2) the maximum activity of the A14Q and N72S mixture was 20% of the wild-type enzyme, in good agreement with the theoretical maximum of 25%; (3) the activity of mutant subunits could not be recovered by mixing with the wild-type subunits; (4) a double mutant, A14Q/N72S, bearing mutations in both putative half-sites was found to inactivate wild-type subunits; (5) the concentration dependence of inactivation by the A14Q/N72S mutant could be well described by a shared site model for a trimeric protein. Unexpectedly, we found that the single mutant D95N behaved in a manner similar to the double mutant, A14Q/N72S, inactivating wild-type subunits. We propose that Asp95 plays a role in more than one active site.

Alanine↗

PubMed1999

The catalytic mechanism of endoplasmic reticulum signal peptidase appears to be distinct from most eubacterial signal peptidases.

Many type I signal peptidases from eubacterial cells appear to contain a serine/lysine catalytic dyad. In contrast, our data show that the signal peptidase complex from the endoplasmic reticulum lacks an apparent catalytic lysine. Instead, a serine, histidine, and two aspartic acids are important for signal peptidase activity by the Sec11p subunit of the yeast signal peptidase complex. Amino acids critical to the eubacterial signal peptidases and Sec11p are, however, positioned similarly along their primary sequences, suggesting the presence of a common structural element(s) near the catalytic sites of these enzymes.

Amino Acid Sequence↗

PubMed1999

Differential expression of MMAC/PTEN in glioblastoma multiforme: relationship to localization and prognosis.

MMAC/PTEN, a tumor suppressor gene located on chromosome 10q, has recently been shown to act as a phosphatidylinositol 3,4,5-triphosphate phosphatase and to modulate cell growth and apoptosis. Somatic mutations of MMAC/PTEN have been reported in a number of human cancers, especially in glioblastoma multiforme (GBM), although the number of identified mutations (approximately 10-35%) is significantly lower than the frequency of LOH affecting the MMAC/PTEN locus in the specimens (approximately 75-95%). To further investigate the possible alterations that may affect MMAC/PTEN, we examined the expression of the gene by reverse transcription-PCR in a series of gliomas. A significant difference (P < 0.001) was observed between the expression of MMAC/PTEN in GBMs versus lower grades of gliomas, thus mimicking the difference in allelic deletion associated with the locus in these tumors. Furthermore, Kaplan-Meier survival plots, adjusted for age and tumor grade, showed a significantly better prognosis for patients whose tumors expressed high levels of MMAC/PTEN. Additionally, immunostaining of GBMs revealed little or no MMAC/PTEN expression in about two-thirds of the tumors, whereas the other approximately one-third of tumors had significantly higher levels of expression. However, in about two-thirds of the high-expressing specimens, a heterogeneous pattern of expression was observed, indicating that certain cells within the tumor failed to express MMAC/PTEN. The combination of these results suggest that, in addition to molecular alterations affecting the gene, altered expression of MMAC/PTEN may play a significant role in the progression of GBM and patient outcome.

Biomarkers, Tumor↗

PubMed1999

[A comparative study of HLA-A locus in northern and southern Chinese by means of PCR/SSOP typing]

OBJECTIVE: To compare the HLA-A locus in a population selected from Beijing (northern group) with that in a population selected from Guangzhou (southern group). METHODS: HLA typing was performed by using PCR/SSOP method. A pair of primer and 54 probes were used. RESULTS: In 18 alleles identified, the differences in gene frequency between northern and southern Chinese were found. In northern group, A*0205, 0210 and 2901 were absent, and the frequencies of A*2601, 3001 and 3101 were higher than those of southern group; while in southern group, A*3103, 3201 and 6801 were absent, the frequencies of A*0203 and 1101 were higher than those of northern group; and in addition, six subtypes of A2 serological specificity, namely A*0201, 0203, 0205, 0206, 0207 and 0210, were found, in which A*0201 predominated. CONCLUSION: There are some differences in the genetic background of northern and southern Chinese. A2 subtypes have important implications for unrelated-donor transplantation.

Journal Article↗

PubMed1999

[The toxicity of combination of selenium, fluoride and arsenic on rat embryos].

Whole embryo rotated culture technique was used to investigate the toxicity of combination of selenium, fluoride and arsenic on rat embryos at day 9.5 of gestation. The result of factorial analysis (3 x 3 x 3) showed that the main effect of combination of selenium, fluoride and arsenic on the developmental toxicity was synergistic. The mixtures with different level of these three chemicals in combination could result in different developmental toxicity. The low level combinations mainly caused teratogenic effect, and the high level combinations(selenium 2.0 micrograms + fluoride 10 micrograms + arsenic 1.0 microgram/ml culture media) caused lethal effect. The results suggested that the disorders of yolk-sac placenta in structure and function were one of teratogenic mechanisms for the combination of selenium, fluoride and arsenic.

Animals↗

PubMed1999

Differential regulation of cellular target genes by p53 devoid of the PXXP motifs with impaired apoptotic activity.

Activation of the p53 tumor suppressor protein can lead to either cell cycle arrest or apoptosis. Several functional domains necessary for mediating cell cycle arrest and apoptosis in p53 have been mapped, e.g., the proline-rich domain. The proline-rich domain is located within residues 60-90, which comprise five PXXP motifs (where P represents proline and X any amino acid). To further delineate the function of the proline-rich domain and its potential role in transactivation, we generated several groups of cell lines that inducibly express various p53 mutants using a tetracycline-regulated expression system. We found that p53(delta62-91), which lacks all five PXXP motifs in human p53, is capable of inducing cell cycle arrest but not apoptosis, while p53(gln22-ser23/delta62-91), which contains a double point mutation in the activation domain as well as deletion of the proline-rich domain, completely loses its activity. However, p53(delta74-91), which contains only one PXXP motif at its N-terminus, is not only capable of inducing cell cycle arrest but also retains a partial apoptotic activity. Furthermore, we found that deletion of the proline-rich region has no or very mild effects on activation of several transiently transfected p53 target gene promoters, i.e., the p21, MDM2, BAX, and GADD45 promoters. However, such deletion differentially affects p53 induction of endogenous target genes, i.e., induction of p21, MDM2, BTG2, p85, PIG3, PIG6 and PIG11 was reduced or abrogated but induction of BAX, KILLER/DR5, PIG2, PIG7 and PIG8 was not substantially affected. Interestingly, induction of GADD45 was enhanced. These results suggest that the proline-rich region may play a role in chromatin remodeling, which counteracts chromatin-mediated repression for some of the endogenous p53 target genes.

Apoptosis↗

PubMed1999

Hormonal prevention of breast cancer: mimicking the protective effect of pregnancy.

Full term pregnancy early in life is the most effective natural protection against breast cancer in women. Rats treated with chemical carcinogen are similarly protected by a previous pregnancy from mammary carcinogenesis. Proliferation and differentiation of the mammary gland does not explain this phenomenon, as shown by the relative ineffectiveness of perphenazine, a potent mitogenic and differentiating agent. Here, we show that short term treatment of nulliparous rats with pregnancy levels of estradiol 17beta and progesterone has high efficacy in protecting them from chemical carcinogen induced mammary cancers. Because the mammary gland is exposed to the highest physiological concentrations of estradiol and progesterone during full term pregnancy, it is these elevated levels of hormones that likely induce protection from mammary cancer. Thus, it appears possible to mimic the protective effects of pregnancy against breast cancer in nulliparous rats by short term specific hormonal intervention.

Animals↗

PubMed1999

Purification, characterization and crystallization of ERA, an essential GTPase from Escherichia coli.

ERA is an essential GTPase widely conserved in bacteria. Homologues of ERA are also present in higher eukaryotic cells. ERA is involved in bacterial cell cycle control at a point preceding cell division. In order to aid the functional investigation of ERA and to facilitate structure-function studies, we have undertaken the X-ray crystallographic analysis of this protein. Here, we report the purification and crystallization procedures and results. The purified ERA exhibits nucleotide-binding activity and GTP-hydrolytic activity. ERA is one of the very few multi-domain GTPases crystallized to date.

Bacterial Proteins↗

PubMed1999

Identification and characterization of a zinc finger gene (ZNF213) from 16p13.3.

During our search for the familial Mediterranean fever (FMF) gene, we identified by cDNA selection a 1.2 kb cDNA fragment representing a novel human gene that is expressed in a wide variety of tissues. This gene spans approx. 8.0 kb genomic DNA and has seven exons. Its 3' untranslated region contains a long tandem repeat that gives rise to a polymorphism with two alleles of approx. 1.1 kb and 1.0 kb, with the 1.1 kb allele in strong linkage disequilibrium with FMF in patients of different ethnic backgrounds. However, both genetic and mutational analyses have excluded this gene as the one responsible for FMF. The predicted 424 amino acid protein, designated ZNF213, contains three C2H2 zinc fingers, a Kruppel associated A box and a leucine rich motif (LeR domain/SCAN box), strongly suggestive of a transcription factor.

Amino Acid Sequence↗

PubMed1999

IFN-alpha 2B enhances Th1 cytokine responses in bladder cancer patients receiving Mycobacterium bovis bacillus Calmette-Guérin immunotherapy.

Combination therapy with intravesical bacillus Calmette-Guérin (BCG) plus IFN-alpha for superficial bladder cancer has been demonstrated to be more effective than either single agent alone in animal studies and of suggested greater efficacy in clinical studies. However, the mechanism by which IFN-alpha enhances BCG-mediated antitumor activity is poorly understood. Using PBMCs from bladder cancer patients, IFN-alpha was found to substantially enhance the efficacy of BCG to induce IFN-gamma production. Among 34 patients tested, 80% showed >4-fold increase. This effect of IFN-alpha was observed in both initial and memory responses to BCG. In addition, IFN-alpha up-regulated BCG-induced IL-12 and TNF-alpha and down-regulated BCG-induced IL-10. Neutralizing endogenous IL-10 or adding exogenous IL-12 provided further synergy for IFN-gamma production. In clinical practice, intravesical IFN-alpha 2B (50 million units (MU)/dose) was observed to accelerate urinary IFN-gamma production to low-dose BCG (one-tenth or one-third of a full dose) in patients treated with combination therapy compared with BCG alone. These results suggest that IFN-alpha is a potent BCG enhancer that polarizes the BCG-induced immune response toward the cellular immune pathway by promoting Th1 cytokine expression and reducing Th2 cytokine expression. This study provides an immunological basis for future rational use of IFN-alpha in conjunction with intravesical BCG for bladder cancer immunotherapy.

Adjuvants, Immunologic↗

PubMed1999

[Significance of collection of chick embryo blood specimen for the determination of hemoglobin folate].

A method for embryo-blood collection (about 100 microliters/embryo) from chorioallantoic blood vessels of day 10 White Leghorn chick embryo was developed and the embryonic hemoglobin folate concentrations (folate/hemoglobin, microgram/g) were measured by the microbiological assay on microtitre dried blood spots to test the hypothesis whether homocysteine (HCY) would increase in folate depletion during early development stage of embryo. The results showed folic acid (FA) and HCY having been placed in the enlarged air cell could quickly pass through inner shell membrane and chorioallantoic membrane, and enter into blood, on the highly vascularized membrane of chick embryo aged 10 days. After 5 micrograms FA were placed on the inner shell membrane, there was a striking increase of hemoglobin folate with a peak in 60 min at 22.26 micrograms/g, followed by a decline. In contrast, 8 mumol of D. L-HCY did not result in the obvious increase of embryonic hemoglobin folate during the total transient time course (0-480 min). By 60 min posttreatment the hemoglobin folate concentration for joint group (HCY 8 mumol + FA 5 micrograms/embryo) had obviously decreased in comparison with single FA group (P < 0.001). The results supported the above hypothesis mentioned. Moreover, both advantages and disadvantages of this method were evaluated.

Animals↗

PubMed1999

Isolation, cloning, and characterization of a new mammalian coronin family member, coroninse, which is regulated within the protein kinase C signaling pathway.

In order to understand the regulatory role of protein kinase C (PKC) in secretory epithelia, it is necessary to identify and characterize specific downstream targets. We previously identified one such protein in studies of gastric parietal cells. This protein was referred to as pp66 because it migrated with an apparent molecular mass of 66 kDa on SDS-polyacrylamide gels. The phosphorylation of pp66 is increased by the cholinergic agonist, carbachol, and by the PKC activator, phorbol-12-myristate-13-acetate, in a calcium-independent manner. In this study, we have purified pp66 to homogeneity and cloned the complete open reading frame. GenBankTM searches revealed a 45% homology with the Dictyostelium actin-binding protein, coronin, and approximately 67% homology with the previously cloned human and bovine coronin-like homologue, p57. pp66 appears to be most highly expressed in the gastrointestinal mucosa and in kidney and lung. Confocal microscopic studies of an enhanced green fluorescent protein fusion construct of pp66 in cultured parietal cells and in Madin-Darby canine kidney cells indicate that pp66 preferentially localizes in F-actin-rich regions. On the basis of our findings, we propose that pp66 may play an important, PKC-dependent role in regulating membrane/cytoskeletal rearrangements in epithelial cells. We have tentatively named this protein coroninse, because it appears to be highly expressed in secretory epithelia.

Amino Acid Sequence↗

PubMed1999

Lesion dimensions during temperature-controlled radiofrequency catheter ablation of left ventricular porcine myocardium: impact of ablation site, electrode size, and convective cooling.

BACKGROUND: It is important to increase lesion size to improve the success rate for radiofrequency ablation of ischemic ventricular tachycardia. This study of radiofrequency ablation, with adjustment of power to approach a preset target temperature, ie, temperature-controlled ablation, explores the effect of catheter-tip length, ablation site, and convective cooling on lesion dimensions. METHODS AND RESULTS: In vitro strips of porcine left ventricular myocardium during different levels of convective cooling and in vivo pig hearts at 2 or 3 left ventricular sites were ablated with 2- to 12-mm-tip catheters. We found increased lesion volume for increased catheter-tip length </=8 mm in vitro (P<0.05) and 6 mm in vivo (P<0. 0001), but no further increase was found for longer tips. For the 4- to 10-mm catheter tips, we found smaller lesion volume in low-flow areas (apex) than in high-flow areas (free wall and septum) (P<0.05). Increasing convective cooling of the catheter tip in vitro increased lesion volume (P<0.0005) for the 4- and 8-mm tips but not for the 12-mm tip as the generator reached maximum output. In contrast to power-controlled ablation, we found a negative correlation between tip temperature reached and lesion volume for applications in which maximum generator output was not achieved (P<0. 0001), whereas delivered power and lesion volume correlated positively (P<0.0001). CONCLUSIONS: Lesion size differs in different left ventricular target sites, which is probably related to convective cooling, as illustrated in vitro. Longer electrode tips increase lesion size for tip lengths </=6 to 8 mm. For temperature-controlled ablation, the tip temperature achieved is a poor predictor of lesion size.

Animals↗

PubMed1999

Enantioselective determination of propafenone and its metabolites in human plasma by liquid chromatography-mass spectrometry.

A sensitive and stereospecific method was developed to determine propafenone (PPF), 5-hydroxypropafenone (5-OHP) as well as their glucuronide and sulfate conjugates in human plasma. Quantitative analyses and preparative isolations of PPF and 5-OHP were performed on a Nucleosil C18 column after liquid-liquid extraction. Afterwards the enantiomeric ratios of PPF and 5-OHP were determined on a Chiral-AGP column with ion trap mass spectrometric detection in the selected reaction monitoring (SRM) mode via electrospray ionization (ESI). The enantiomers of PPF and 5-OHP were separated with different mobile phases. For PPF enantiomers, the mobile phase consisted of 10 mM ammonium acetate buffer (pH 5.96)-1-propanol (100:9, v/v), at a flow-rate of 0.5 ml/min; And for 5-OHP enantiomers, the mobile phase was 10 mM ammonium acetate buffer (pH 4.1)-2-propanol (100:0.9, v/v), at a flow-rate of 0.6 ml/min. The SRM transitions m/z 342 to m/z 324 and m/z 358 to m/z 340 were monitored for detection of enantiomers of PPF and 5-OHP, respectively. Linear calibration curves were obtained in the concentration range of 20-1600 ng/ml for each enantiomer of PPF and 20-500 ng/ml for the 5-OHP enantiomer. The limits of quantification for each enantiomer of PPF and 5-OHP were found to be 20 ng/ml. Precision and accuracy were within 11% over the calibration range for each of the analytes. Incubation of the plasma samples with beta-glucuronidase/arylsulfatase and the use of the specific beta-glucuronidase inhibitor saccharo-1,4-lactone allows the quantitation of both the glucuronide and sulfate conjugates of the enantiomers. The method was applied to human plasma samples from ten Chinese male volunteers after oral administration of 300 mg racemic propafenone.

Anti-Arrhythmia Agents↗