Browsing by Author "VALENZUELA, P"

Now showing 1 - 13 of 13
  • No Thumbnail Available
    Item
    CELL-FREE SYNTHESIS OF ACETYLCHOLINE-RECEPTOR POLYPEPTIDES
    (1980) MENDEZ, B; VALENZUELA, P; MARTIAL, JA; BAXTER, JD
  • No Thumbnail Available
    Item
    CHEMICAL MODIFICATION OF LYSYL AND CYSTEINYL RESIDUES OF YEAST RNA POLYMERASE-I
    (1981) BULL, P; ZALDIVAR, J; WYNEKEN, U; VENEGAS, A; VALENZUELA, P
    The active site of yeast RNA polymerase I was studied using pyridoxal 5''-phosphate, p-chloromercuribenzoate and 5,5''-dithiobis (2-nitrobenzoate) as modifying agents. The enzyme was rapidly inactivated by pyridoxal 5''-phosphate, by formation of a Schiff base between the aldehyde group and lysine amino groups of the enzyme, located in the largest subunit. Out of 45 SH groups, 2 are required for enzyme activity. Since they were partially protected by substrates and DNA, they may be at the active site. A hypothetical model of catalysis is proposed based on the results presented.
  • No Thumbnail Available
    Item
    EFFECTS OF CAPTOPRIL VERSUS MILRINONE THERAPY IN MODULATING THE ADRENERGIC NERVOUS-SYSTEM RESPONSE TO EXERCISE IN CONGESTIVE HEART-FAILURE
    (1990) CORBALAN, R; JALIL, J; CHAMORRO, G; CASANEGRA, P; VALENZUELA, P
    The potential adverse consequences of increased adrenergic nervous system activity in patients with heart failure are now recognized. Modulation of the plasma noradrenaline response to submaximal exercise should be desirable. The long-term (9 weeks) effects of milrinone (10 mg 4 times a day) or captopril (50 mg 3 times a day) compared to placebo were evaluated in a double-blind crossover study, in 16 patients with stable, congestive heart failure receiving digoxin and furosemide. After treatment, clinical status (score range 0 to 14 points) improved significantly with both milrinone (4.4 .+-. 0.5, p < 0.01) and captopril (4.1 .+-. 0.4, p < 0.01). Plasma noradrenaline at rest was similar with both drugs and not significantly different from placebo. During submaximal exercise it increased significantly to 1,295 .+-. 174 pg/ml with milrinone; this response was reduced significantly with captopril, to 820 .+-. 100 pg/ml (p < 0.01). Thus, long-term therapy with both captopril and milrinone improved the clinical score, but only captopril reduced the plasma noradrenaline response to submaximal exercise. These findings suggest that angiotensin-enzyme inhibition with captopril will modulate the adrenergic system response to daily activities in patients with chronic congestive heart failure and therefore could have additional salutary effects beyond vasodilatation.
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
    ISOLATION AND STRUCTURE OF A YEAST INITIATOR TRANSFER RNA-MET GENE
    (1982) VENEGAS, A; GONZALEZ, E; BULL, P; VALENZUELA, P
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
    OVERDOSE OF COLCHICINE IN A 3-YEAR-OLD CHILD
    (1995) VALENZUELA, P; PARIS, E; OBERPAUER, B; RIOS, JC; CONCHA, F
    We report the case of a previously healthy girl who developed a multi-systemic failure after an inappropriate dose of colchicine. The patient recovered completely and had no residual effects.
  • No Thumbnail Available
    Item
    PHYSICAL CHARACTERIZATION OF A PLASMID (PTT1) ISOLATED FROM THERMUS THERMOPHILUS
    (1981) EBERHARD, MD; VASQUEZ, C; VALENZUELA, P; VICUNA, R; YUDELEVICH, A
  • No Thumbnail Available
    Item
    STRUCTURE OF THE EUKARYOTIC GENOME - A UNIQUE PSEUDOGENE LACKING INTRONS AND POLY-A TAIL AS A MEMBER OF THE HUMAN BETA-TUBULIN GENE FAMILY
    (1982) PICHUANTES, S; MEDINA, A; BELL, G; GOMEZ, I; VALENZUELA, P; BULL, P; VENEGAS, A
    From a human gene bank constructed in the vector phage Charon 4A, 14 clones carrying complementary sequences to .alpha. and .beta. tubulin chicken c[complementary]DNA were isolated. A preliminary structural analysis of some of the .beta. clones, based on restriction digests followed by Southern hybridization, allowed us to select clone .beta.9 as the one containing a functional gene. After further analysis this clone was proved to contain a pseudogene. The coding sequence is altered by 4 stop codons, 6 short delections and 2 1-base insertions. These changes prevent any correct translation. The pseudogene seems to preserve some vestigial control regions and does not contain introns. No in vitro RNA synthesis directed by this clone was detected.
  • No Thumbnail Available
    Item
    SUBUNITS OF YEAST RNA POLYMERASE-I INVOLVED IN INTERACTIONS WITH DNA AND NUCLEOTIDES
    (1978) VALENZUELA, P; BULL, P; ZALDIVAR, J; VENEGAS, A; MARTIAL, J
    Reaction of yeast [Saccharomyces cerevisiae] RNA polymerase I with pyridoxal 5''-phosphate and sodium borohydride under conditions which inactivate the enzyme results in the specific binding of pyridoxal 5''-phosphate to subunits of 185,000, 137,000, 48,000 and 36,000 daltons. Nucleotides, which protect the enzyme from inactivation specifically inhibit the binding of pyridoxal 5''-phosphate to subunits of 185,000 and 137,000 daltons. DNA which also protects the enzyme from inactivation by pyridoxal 5''-phosphate prevents the binding of the reagent to the 4 polypeptides. These results suggest that subunits of 185,000 and 137,000 are involved in interactions with both nucleotides and DNA presumably of the type leading to initiation and/or polymerization and that subunits of 48,000 and 36,000 daltons also bind to DNA but this interaction is not strictly required for polymerase activity.
  • No Thumbnail Available
    Item
    THE PH-DEPENDENCE OF RAT-LIVER RNA POLYMERASE-I AND POLYMERASE-II
    (1980) BULL, P; MARTIAL, J; TELLEZ, R; VENEGAS, A; VALENZUELA, P
    The effect of pH on the stability and activity of rat liver RNA polymerases I (A) and II (B) was studied. Both enzymes are irreversibly inactivated in buffer solutions below pH 5.0. Km values of the 2 enzymes are constant between pH 6.5 and 8.7, but a 2- to 3-fold increase is observed between pH 8.7 and 9.7. The Vmax vs. pH profiles are bell-shaped curves indicating the participation of 2 ionizing groups with apparent pKa values of 6.5 and 9.8 for enzyme I and 6.7 and 9.9 for enzyme II. Both enzymes are inactivated by photooxidation in the presence of Rose Bengal. The above pKa corresponds to the imidazole of a histidine residue and an amino group of a lysine residue.
  • No Thumbnail Available
    Item
    THE YEAST TRANSFER RNAPHE GENE FAMILY - STRUCTURES AND TRANSCRIPTIONAL ACTIVITIES REVEAL MEMBER DIFFERENCES NOT EXPLAINED BY INTRAGENIC PROMOTERS
    (1987) BULL, P; THORIKAY, M; MOENNE, A; WILKENS, M; SANCHEZ, H; VALENZUELA, P; VENEGAS, A
  • No Thumbnail Available
    Item
    YEAST RNA-POLYMERASE .1. A EUKARYOTIC ZINC METALLOENZYME
    (1976) AULD, DS; ATSUYA, I; CAMPINO, C; VALENZUELA, P
    Microwave excitation spectrometry and metal binding inhibition studies showed that Zn is a catalytically essential component of the highly purified RNA polymerase I from yeast, the 1st eukaryotic RNA polymerase I available in quantities sufficient for such studies. It contained 2.4 g-atom of Zn based on a MW of 6.5 .times. 105. Cu, Fe, Mn and Mg were absent, i.e., below the limits of detection, 10-3-10-14 g-atoms. A number of derivatives of 1,10-phenanthroline reversibly inhibited the polymerase catalyzed reaction, apparently by forming a ternary polymerase.cntdot.Zn.cntdot.OP complex while the nonchelating isomer, 1,7-phenanthroline, was ineffective.