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Y Tam

Publications and source records attributed to Y Tam.

13 recordsLinked to original sources
PubMed2006

The complete nucleotide sequence of Passiflora latent virus and its phylogenetic relationship to other carlaviruses.

A virus identified as Passiflora latent virus (PLV) was isolated from passion fruit plants. Particle morphology, host range and serological properties suggested that this virus belongs to the genus Carlavirus. The complete genomic sequence of PLV was determined by sequencing overlapping cDNA fragments. The genome consisted of 8386 nt, excluding the poly (A) tail and contained six open reading frames, typical of carlaviruses. The overall similarities of the predicted amino acid sequence of PLV to those of other carlaviruses ranged from 25 to 73%. Phylogenetic analysis indicated that PLV was closely related to lily symptomless virus and blueberry scorch virus. This is the first report of the complete nucleotide sequence and genome structure of PLV.

Base Sequence↗
PubMed1999

An HPLC method for the determination of diastereomeric prodrug RS-79070-004 in human plasma.

Ganciclovir is an antiviral nucleoside analogue approved for treatment and prevention of cytomegalovirus infections in immunocompromised subjects. RS-79070-194, a diastereomeric monovalyl ester of ganciclovir (hydrochloride salt), is under evaluation as a prodrug to increase the bioavailability of ganciclovir. An HPLC method with column switching has been developed and validated for quantification of the corresponding free base RS-79070-004 in human plasma. In the method, proteinaceous material in 0.25 ml of plasma is precipitated by trichloroacetic acid. An aliquot of the supernatant is analyzed by HPLC, with automated column switching to remove late-eluting materials that might interfere with the analyte peaks in subsequent runs. Detection of RS-79070-004 is by UV lambda = 254 nm). The peak areas for each isomer are summed to generate a value for total RS-79070-004. The method has a validated range of 0.0400-4.00 microg/ml and a lower limit of quantification of 0.0400 microg/ml. All intra- and inter-assay %CVs were < 7.5%, and all recoveries (accuracy) were within 6% of nominal values. No interference was observed by ganciclovir, caffeine, acetaminophen, or ibuprofen. Analyte stability in plasma and in the sample extracts is adequate for the specified collection, storage, and analysis conditions. The validated method has been successfully used to analyze clinical study samples.

Antiviral Agents↗
PubMed1998

Heat-shock-induced assembly of Hsp30 family members into high molecular weight aggregates in Xenopus laevis cultured cells.

In this study, we have examined whether members of the small heat shock protein family, hsp 30, were capable of forming heat-induced aggregates in Xenopus laevis A6 kidney epithelial cells. Rate-zonal centrifugation coupled with immunoblot analysis demonstrated the presence of hsp30 aggregates with an estimated sedimentation coefficient of 10-16S. Also, pore exclusion limit electrophoretic analysis of labeled protein from heat-shocked A6 cells revealed four heat-induced aggregates, including a prominent 510 kDa aggregate, as well as weaker 350, 290, and 240 kDa aggregates. Immunoblot analysis of the aggregates employing an hsp30C antibody suggested that the 510 and 350 kDa aggregates were comprised of hsp30 protein. One- and two-dimensional SDS-PAGE analysis of the proteins isolated from the 510 kDa region of the pore exclusion limit electrophoretic gel confirmed the presence of 30 kDa heat-induced protein. A total of eight small hsps were present in this aggregate, suggesting that virtually all of the major small hsps in Xenopus A6 cells were involved in aggregate formation. This study also detected the presence of heat-inducible hsp70 in the 510 kDa gel fraction containing the small hsps, but it could not be determined whether it was part of the multimer complex.

Animals↗
PubMed1998

Ferrous sulphate interacts with captopril.

AIMS: To determine if iron binds strongly to captopril and reduces captopril absorption. METHODS: A variety of in vitro experiments was conducted to examine iron binding to captopril and a randomized, double-blind, placebo controlled, cross-over study design was used to assess the in vivo interaction. Captopril (25 mg) was coingested with either ferrous sulphate (300 mg) or placebo by seven healthy adult volunteers. Subjects were phlebotomized and had blood pressure measured at 0, 0.25, 0.5, 1, 2, 4, 6, 8, and 12 h post ingestion. A 1 week washout period was used. RESULTS: The coingestion of ferrous sulphate and captopril was associated with a 37% (134 ng ml(-1) h, 95% CI 41-228 ng ml(-1) h, P = 0.03) decrease in area under the curve (AUC) for unconjugated plasma captopril. There were no substantial changes in Cmax (mean difference; -32; 95% CI -124-62 ng ml(-1) (P = 0.57)) or in tmax (mean difference; 0; 95% CI -18-18 min (P = 0.65)) for unconjugated captopril when captopril was ingested with iron. There was a statistically insignificant increase in AUC for total plasma captopril of 43% (1312 ng ml(-1) h, 95% CI -827-3451 ng ml(-1) h P = 0.27) when captopril was ingested with iron. The addition of ferric chloride to captopril resulted in the initial rapid formation of a soluble blue complex which rapidly disappeared to be replaced by a white precipitant. The white precipitate was identified as captopril disulphide dimer. There were no significant differences in systolic and diastolic blood pressures between the treatment and placebo groups. CONCLUSIONS: Co-administration of ferrous sulphate and iron results in decreased unconjugated captopril levels likely due to a chemical interaction between ferric ion and captopril in the gastrointestinal tract. Care is required when coprescribing captopril and iron salts.

Adult↗
PubMed1998

Characterization of a novel group of basic small heat shock proteins in Xenopus laevis A6 kidney epithelial cells.

In this study, we report the detection of a new group of five stress-inducible basic small heat shock proteins (BShsps) in Xenopus laevis kidney epithelial A6 cells by means of two-dimensional non-equilibrium pH gradient gel electrophoresis. These basic 30-kDa small hsps are distinct from the previously described X. laevis acidic hsp30 family on the basis of their charge and lack of cross-reactivity with an hsp30 antibody. Furthermore, at least two of the five BShsps were present constitutively, an observation that has not been made with the acidic hsp30 family. The heat inducibility of the BShsps was regulated at the level of transcription as indicated by their inhibited synthesis in the presence of the transcriptional inhibitor actinomycin D. Furthermore, the optimal temperature of BShsp induction, temporal pattern of synthesis, and induction of BShsps by other stressors such as herbimycin A and sodium arsenite were similar to those reported for the acidic hsp30 family. This study suggests that X. laevis contains at least two unique groups of small heat shock proteins that are coordinately expressed.

Animals↗
PubMed1997

Heat shock protein gene expression during Xenopus development.

Stress-induced heat shock protein gene expression is developmentally regulated during early embryogenesis of the frog, Xenopus laevis. For example, a number of heat shock protein genes, such as hsp70, hsp90, and ubiquitin are not heat-inducible until after the midblastula stage of embryogenesis. Furthermore, the family of small heat shock protein genes, hsp30, are differentially expressed after the midblastula stage as well as being regulated at the level of mRNA stability. Many of these stress proteins are also synthesized constitutively during oogenesis and embryogenesis during which they may act as molecular chaperones as well as being involved in sequestering proteins in an inactive state until required by the developing embryo. Furthermore the induction of these stress protein genes has been correlated with enhanced thermoresistance. During stressful conditions heat shock proteins probably prevent aggregation or misfolding of damaged proteins within the embryo.

Animals↗
PubMed1996

Chiral kinetics and dynamics of ketorolac.

It has been shown that the analgesic and cyclooxygenase inhibitor activity of ketorolac tromethamine (KT), which is marketed as the racemic mixture of (-)S and (+)R enantiomers, resides primarily with (-)S ketorolac and that the ulcerogenic activity of this agent also resides in (-)S ketorolac. Resolution of individual enantiomers for analysis in plasma samples has been accomplished by two methods: derivatization to form diastereomers that are separated by HPLC, or direct HPLC using a chiral phase column. When mice and rats were given oral solutions of (-)S and (+) KT, it was found that the kinetics and interconversion of the enantiomers were species and dose dependent. Interconversion was higher in mice than in rats; when (-)S KT was administered, 71% of the area under the concentration-time curve (AUC) was due to (+)R ketorolac in mice, compared with 12% in rats. More interconversion was observed at higher doses; the percent of AUC due to (-)S ketorolac when (+)R KT was administered increased from 12% to 25% in mice and from 2% to 8% in rats. In general, more interconversion occurred from (-)S to (+)R ketorolac in the animal studies. Human subjects were given single oral solution doses of racemic KT (30 mg), (-)S KT (15 mg), and (+)R KT (15 mg). The plasma concentrations of (-)S ketorolac were lower than (+)R ketorolac at all sample times after racemic KT (22% of the AUC was due to (-)S ketorolac). When (+)R KT was administered, (-)S ketorolac was not detectable and interconversion was essentially 0%. When (-)S KT was administered, significant levels of (+)R ketorolac were detectable and interconversion was 6.5%. After all doses, plasma half-life was shorter and clearance greater for (-)S ketorolac than for (+)R ketorolac. Thus, in humans very little or no interconversion of (+)R to (-)S was observed, and interconversion of (-)S to (+)R was minimal (6.5%). These data demonstrate that the kinetics and interconversion of the enantiomers of ketorolac is different in animals and humans as well as from most other NSAIDs. This may be due to more rapid excretion or metabolism of (-)S ketorolac and a different mechanism of interconversion.

Animals↗
PubMed1995

Identification of members of the HSP30 small heat shock protein family and characterization of their developmental regulation in heat-shocked Xenopus laevis embryos.

In the present study we have characterized the synthesis of members of the HSP30 family during Xenopus laevis development using a polyclonal antipeptide antibody derived from the carboxyl end of HSP30C. Two-dimensional PAGE/immunoblot analysis was unable to detect any heat-inducible small HSPs in cleavage, blastula, gastrula, or neurula stage embryos. However, heat-inducible accumulation of a single protein was first detectable in early tailbud embryos with an additional 5 HSPs at the late tailbud stage and a total of 13 small HSPs at the early tadpole stage. In the Xenopus A6 kidney epithelial cell line, a total of eight heat-inducible small HSPs were detected by this antibody. Comparison of the pattern of protein synthesis in embryos and somatic cells revealed a number of common and unique heat inducible proteins in Xenopus embryos and cultured kidney epithelial cells. To specifically identify the protein product of the HSP30C gene, we made a chimeric gene construct with the Xenopus HSP30C coding sequence under the control of a constitutive promoter. This construct was microinjected into fertilized eggs and resulted in the premature and constitutive synthesis of the HSP30C protein in gastrula stage embryos. Through a series of mixing experiments, we were able to specifically identify the protein encoded by the HSP30C gene in embryos and somatic cells and to conclude that HSP30C synthesis was first head-inducible at the early tailbud stage of development. The differential pattern of heat-inducible accumulation of members of the HSP30 family during Xenopus development suggests that these proteins may have distinct functions at specific embryonic stages during a stress response.

Amino Acid Sequence↗
PubMed1995

Methyldopa kinetics before and after ingestion of methyldopa for eight weeks.

Methyldopa urine and plasma levels and urine metabolite levels were assessed following intravenous (IV) and oral (PO) methyldopa before, and after ingestion of methyldopa (500 mg) daily for eight weeks. There was no increase in (estimated) methyldopa absorption (8.4%) or renal clearance (PO 13.9%, IV 2.33%) after the eight weeks of methyldopa ingestion. However, the initial methyldopa absorption and renal clearance values in this study were higher than that in previous studies. There was an inverse relation between the initial methyldopa absorption and the change in absorption (r - 0.605) and between the initial methyldopa renal clearance and the change in renal clearance (PO r -0.874, IV r -0.891). Overall, this study did not confirm our previous studies showing induction of methyldopa absorption and renal clearance, possibly due to prior up regulation of transporter function. Consistent with methyldopa inducing drug transporters, those with low initial absorption and renal clearance values had the greatest increases.

Absorption↗
PubMed1992

Enzyme-linked immunosorbent assay for the detection of substances that carry blood group A specificity.

An enzyme-linked immunosorbent assay (ELISA) was developed to estimate the amount of material carrying blood group A activity in biologic samples. A soluble synthetic form of the A antigenic determinant (A trisaccharide, ATS) conjugated to peroxidase competes with the blood group A substance present in a biologic sample for anti-A attached to a solid phase by a second antibody coating the plastic micro-wells. A reference curve is constructed by using known quantities of ATS to compete with a fixed amount of ATS-peroxidase conjugate. The A substance activity in a sample is obtained by extrapolating the degree of inhibition of the binding of the ATS-peroxidase conjugate to an equivalent amount of ATS in the reference curve. The assay is reproducible, specific, and sensitive. It has been used in pharmacologic studies to estimate the concentration of ATS in the blood and urine of rats, rabbits, and baboons and in a study with human samples, testing the potential clinical use of ATS to neutralize anti-A when therapeutically indicated. It is also useful for the detection of ABO natural products in secretions, thus allowing the accurate classification of secretor and nonsecretor individuals.

ABO Blood-Group System↗
PubMed1991

A chronic conscious dog model for direct transhepatic studies in normal and pancreatic islet cell transplanted dogs.

A chronic conscious, large mammal model for repeated transhepatic studies over a period of 6-8 weeks has been developed for application to the study of the hepatic effects of pancreatic hormone secretion and glucose metabolism, studies of the hepatic mechanisms associated with high first-pass drug metabolism and food interactions, and studies of insulin balance in dogs that have undergone previous pancreatectomy and islet cell auto-transplantation. The preparation of specialized blood sampling catheters and blood flow probes, surgical preparations, pre- and postoperative care, catheter maintenance, and possible complications are described. Data from an oral glucose meal (OMT) are presented. Frequent blood samples from portal, hepatic and jugular veins, and carotid artery were collected and analyzed for plasma insulin concentrations (IRI) and glucose. IRI fluxes were determined for each time period by interpolation of flux X time curves. Total IRI flux was determined as the sum of the areas under the curves for each sampling period. Hepatic insulin extraction was calculated for each sampling interval. By this method of analysis, it was possible to determine hepatic IRI extraction during non-steady-state conditions. The techniques described in the development of this complex animal model, which allows for repeated transhepatic studies in the same conscious subject, may also have application in other chronic studies involving organs other than the liver.

Animals↗
PubMed1988

Increased efficacy and toxicity of lidocaine in patients on beta-blockers.

The greatest differences in ventricular arrhythmias and adverse effects of lidocaine observed in this study were between patients on both lidocaine and a beta-adrenoceptor blocking agent and those on neither drug. Although free fractions of lidocaine and methylglycylxylidine tended to be higher in patients on beta-adrenoceptor blocking agents, this difference was not significant nor were any other differences in serum drug levels observed.

Adrenergic beta-Antagonists↗