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Biomedical subjects

R Wei

Publications and source records attributed to R Wei.

At least 55 records · Page 3Linked to original sources
PubMed1988

The HAP3 regulatory locus of Saccharomyces cerevisiae encodes divergent overlapping transcripts.

Activation of the CYC1 upstream activation site, UAS2, and transcription of several other genes encoding respiratory functions requires the product of the regulatory gene HAP2. We report here the isolation and characterization of a second UAS2 regulatory gene, HAP3. Like mutations in HAP2, a mutation in HAP3 abolishes the activity of UAS2 and prevents growth on nonfermentable carbon sources. The HAP3 gene was cloned and, surprisingly, was found to encode two divergently transcribed, overlapping transcripts: a 570-base RNA and a 3-kilobase (kb) RNA. Chromosomal disruption experiments defined the critical region for HAP3 function to a 1.3-kb segment in which the two transcripts overlap. Analysis of the HAP3 DNA sequence showed that the 570-base transcript could encode a protein of 144 amino acids. Synthesis of the 144-amino-acid protein under regulatory control in vivo demonstrated that this protein is essential for activity of UAS2 as well as for growth on nonfermentable carbon sources. The largest open reading frame in the critical region of the 3-kb transcript is only 86 amino acids. Using site-directed mutagenesis, we demonstrated that the 86-amino-acid open reading frame was not involved in UAS2 activity. The possible role of this 3-kb antisense RNA in HAP3 expression or function is discussed.

Amino Acid Sequence↗
PubMed1986

Two or more copies of Drosophila heat shock consensus sequence serve to activate transcription in yeast.

A synthetic oligonucleotide bearing the Drosophila heat shock consensus sequence confers heat inducibility on a CYC1-lacZ gene in Saccharomyces cerevisiae. This sequence CTGGAATTTTCTAGA was inserted in place of the upstream activation sites of the CYC1 promoter adjacent to CYC1 TATA boxes. These constructs were transformed into yeast and found to be heat-inducible when two or more inserts were present. The level of inducibility seemed to increase with the number of inserted sequences: however, the orientations of these sequences relative to each other did not have much effect.

Animals↗
PubMed1986

Measurement of total HDL, HDL2 and HDL3 by dextran sulfate-MgCl2 precipitation technique in human serum.

We describe a simple and reliable method for determination of total HDL, HDL2, and HDL3 by a precipitation technique using dextran-sulfate (Mr 50,000)-Mg2+. A combined solution of dextran sulfate and Mg2+ at their respective final concentration of 0.9 g/l and 27 mmol/l was optimal for separating total HDL from the other lipoproteins. The present method compares favorably with a heparin-MnCl method (r = 0.998). The HDL was further resolved into HDL2 and HDL3 by addition of a combined solution of dextran sulfate and Mg2+ (1.5 m/l and 10 g/l) to the total HDL solution. Comparison of this precipitation method with the well-established ultracentrifugation method yielded the mean correlation coefficient of 0.941 and 0.869 for HDL2 and HDL3, respectively.

Chemical Precipitation↗
PubMed1985

Mucin biosynthesis. Properties of a bovine tracheal mucin beta-6-N-acetylglucosaminyltransferase.

We have characterized a bovine tracheal mucin beta-6-N-acetylglucosaminyltransferase that catalyses the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to the C-6 of the N-acetylgalactosamine residue of galactosyl-beta 1----3-N-acetylgalactosamine. Optimal enzyme activity was obtained between pH 7.5-8.5, at 5mM-MnCl2, and at 0.06-0.08% (v/v) Triton X-100 (or Nonidet P-40), or 0.5-5.0% (v/v) Tween 20. Ba2+, Mg2+ and Ca2+ could partially replace Mn2+, but Co2+, Fe2+, Cd2+ and Zn2+ could not. Sodium dodecyl sulphate, cetylpyridinium chloride, sodium deoxycholate, octyl beta-D-glucoside, digitonin and alkyl alcohols were less effective in enhancing enzyme activity, and dimethyl sulphoxide was ineffective. The apparent Michaelis constants were 1.25 mM for UDP-N-acetylglucosamine, 0.94-3.34 mM for freezing-point-depressing glycoprotein and 0.19 mM for periodate-treated blood-group-A porcine submaxillary mucin. Asialo ovine submaxillary mucin could not serve as the glycosyl acceptor. The structure of the 14C-labelled oligosaccharide obtained by alkaline-borohydride treatment of the product was identified as Gal beta 1----3(Glc-NAc beta 1----6)N-acetylgalactosaminitol by beta-hexosaminidase treatment, gas chromatography-mass spectrometry and 1H-n.m.r. (270 MHz) analysis. The enzyme is important in the regulation of mucin oligosaccharide biosynthesis.

Alcohols↗
PubMed1985

Properties of creatine kinase-BB from canine and human brain tissues.

Creatine kinase (EC 2.7.3.2) BB isoenzyme (CK-BB) was purified to homogeneity from canine and human brain tissues. The purified protein from both sources exhibits Mr of 84,700 daltons. The canine isoenzyme exhibits several properties similar to human isoenzyme with respect to reactive and total thiol groups, UV spectra, isoelectric points and reaction kinetics. While both canine and human CK-BB isoenzymes are unstable compared to other CK isoenzymes, canine CK-BB is even less stable than the human enzyme, losing most of its activity within 20 h at 4 degrees C at pH 5.0. Addition of 2-mercaptoethanol does not prevent rapid loss of the enzyme activity. Increasing the pH to 9.0, however, increases the stability of both CK-BB isoenzymes. Agarose electrophoresis demonstrated the presence of MM as well as BB isoenzyme in various parts of brain tissues. BB was present at an activity of 90.8-93.3 U/mg and MM at 6.7-9.2 U/mg.

Animals↗
PubMed1984

Purification of creatine kinase-BB isoenzymes from human and canine tissues.

We describe a procedure for the purification of creatine kinase BB isoenzyme from canine and human brain tissue. The purification involves sequentially 50-70% (NH4)2SO4 fractionation, DEAE-Sephacel, Blue-Sepharose CL-6B, and chromatofocusing chromatography. This method produces a homogeneous protein purification as verified by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing chromatography.

Animals↗
PubMed1984

Inaccuracy of estimated creatinine clearance for prediction of iothalamate glomerular filtration rate.

The clinical practice of estimating creatinine clearance (Ccr) from a patient's serum creatinine value by use of various nomograms and prediction formulas is widespread. The predictive accuracy of such Ccr estimates as substitutes for measured values of glomerular filtration rate (GFR) has not been determined. In addition, the effect of patient physical parameters on GFR prediction accuracy has not been assessed. To investigate these issues, 500 predicted Ccr values from each of four versions of the formula of Cockcroft and Gault were statistically compared with GFR values measured by sodium iothalamate clearance (Cio) in 394 human subjects representing every level of renal function. We conclude that (1) the original formula of Cockcroft and Gault is an inaccurate predictor of GFR; (2) correction of the formula for patient physical parameters does improve its accuracy for GFR prediction; (3) the best formula is not accurate enough to replace laboratory measurement of GFR; and (4) GFR prediction inaccuracy is more often associated with extremes in patient age, weight, serum creatinine, body surface area, and measured GFR but may occur for any value of each of these parameters.

Adult↗
PubMed1979

Genetic effects of PR toxin in eukaryotic microorganisms.

The genetic activity of PR toxin, a mycotoxin from Penicillium roqueforti, was studied in Saccharomyces cerevisiae and Neurospora crassa. The results show that PR toxin, without enzymic activation, causes gene conversion in S. cerevisiae strains D4 and D7, reverse mutation in S. cerevisiae strain D7 and N. crassa strain N24, and mitotic crossing-over in S. cerevisiae strain D7, In the log phase cells of S. cerevisiae the effects are more pronounced at alkaline than at acid pH. The active site responsible for the genetic activity and toxicity is known. The carbonyl groups appear to play an important role in the biologic activity of this molecule.

Chromosomes↗
PubMed1977

Phospholipase C-labeled anti-human IgG: inhibition by human IgF.

We report here the inhibition of enzyme activity of phospholipase C-anti-human rabbit IgG conjugate complexed with human IgG. Phospholipase C activity was measured by assaying the release of hemoglobin from erythrocytes. The degree of inhibition varies depending on the relative amount of IgG utilized. A water soluble carbodiimide linking yields a conjugate which is inhibited by IgG, while conjugate prepared by glutaraldehyde is not. Immunodiagnostic assays requiring detection of low levels of antigen or antibody may be possible utilizing the phospholipase C-erythrocyte technique.

Animals↗
PubMed1977

Preparation of a phospholipase C-antihuman IgG conjugate, and inhibition of its enzymatic activity by human IgG.

We labeled IgG with phospholipase C, using 1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide. Enzymaticactivity of the resulting conjugate was inhibited when it was complexed with human IgG, but rabbit or goat IgG was not effective in suppressing the enzyme activity. Normal erythrocytes were used as substrate for the enzyme, enzymatic activity being assessed by measuring the release of hemoglobin. The substrates for phospholipase C are phospholipids, which are major components of the erythrocyte membranes. Hence, the phospholipids in the membranes are viewed as being "immobilized." Perhpas such immobilization of substrate may be a requisite to the inhibition phenomenon.

Animals↗
PubMed1977

Solid-phase enzyme immunoassay for hepatitis B surface antigen.

A solid-phase enzyme immunoassay is described for measuring hepatitis B surface antigen in human serum or plasma. Immunologically purified antibody labeled with horseradish peroxidase was used as the indicator. In the assay system, antibody-coated controlled-pore glass is used as a solid support and there are three sequential incubations, totaling 2 h, at room temperature. Results for serially diluted positive and reference sera compare favorably to radioimmunoassay in sensitivity and specificity.

False Positive Reactions↗
PubMed1975

Liposome spin immunoassay: a new sensitive method for detecting lipid substances in aqueous media.

A new sensitive immunoassay procedure is described for quantitative detection of glycolipids and other lipids in aqueous media. As with other immunoassays specific antiserum is first reacted with the free lipid hapten. The amount of antibody activity remaining is measured by assaying the release, in the presence of complement, of spin label marker from liposomes containing the same lipid hapten. Using this method, 2.6 pmol of aqueous Forssman hapten was detected, and the sensitivity could be increased further.

Antigen-Antibody Reactions↗