Biomedical subjects

R Tinoco

Publications and source records attributed to R Tinoco.

10 recordsLinked to original sources

PubMed2002

Enhanced activity by poly(ethylene glycol) modification of Coriolopsis gallica laccase.

We are studying the enzymatic modification of polycyclic aromatic hydrocarbons (PAHs) by the laccase from Coriolopsis gallica UAMH 8260. The enzyme was produced during growth in a stirred tank reactor to 15 units ml(-1), among the highest levels described for a wild-type fungus; the enzyme was the major protein produced under these conditions. After purification, it exhibited characteristics typical of a white rot fungal laccase. Fifteen azo and phenolic compounds at 1 mM concentration were tested as mediators in the laccase oxidation of anthracene. Higher anthracene oxidation was obtained with the mediator combination of ABTS and HBT, showing a correlation between the oxidation rate and the mediator concentration. Reactions with substituted phenols and anilines, conventional laccase substrates, and PAHs were compared using the native laccase and enzyme preparations chemically modified with 5000 MW-poly(ethylene glycol). Chemically modified laccase oxidized a similar range of substituted phenols as the native enzyme but with a higher catalytic efficiency. The k(cat) increase by the chemical modification may be as great as 1300 times for syringaldazine oxidation. No effect was found of chemical modification on mediated PAH oxidation. Both unmodified and PEG-modified laccases increased PAH oxidation up to 1000 times in the presence of radical mediators. Thus, a change of the protein surface improves the mediator oxidation efficiency, but does not affect non-enzymatic PAH oxidation by oxidized mediators.

Amino Acid Sequence↗

PubMed2002

Field trial of the brucellosis fluorescence polarization assay.

Fluorescence polarization assay (FPA) is a homogeneous technique which was applied to the serological diagnosis of bovine brucellosis. Because of its simplicity and because it may be performed very rapidly, it was an ideal test to adapt to field use. The FPA was used to test cattle on six dairy farms in Baja California, Mexico. Anticoagulated blood, serum, and milk were collected from each animal. The anticoagulated blood was tested immediately on the farm while serum and milk were tested subsequently in the laboratory. Cattle on one farm (n = 140) were thought not to be infected with Brucella abortus and the other farms were thought to have high prevalence of the infection. The whole blood FPA (FPA(bld)) did not detect antibody in any of the cattle on the first premise. This finding was confirmed using a number of other serological tests, including the buffered antigen plate agglutination test, the complement fixation test, the indirect and competitive enzyme immunoassays, and the FPA using serum and milk. Cattle on the other premises (n = 1122) were tested in a similar fashion. The sensitivity of the FPA(bld), relative to the serum FPA (considered the definitive test), was 99.1% and the relative specificity of the FPA(bld) was 99.6%. These results compared favourably with those obtained using the other serological tests.

Animals↗

PubMed2001

Kinetic differences of purified laccases from six Pleurotus ostreatus strains.

AIMS: Enzyme kinetics of purified laccases from six different Pleurotus ostreatus strains were determined in the oxidation of syringaldazine, guaiacol and ABTS. METHODS AND RESULTS: Significant differences in the kinetic constants were found. Catalytic activity (kcat) ranged from 19 to 941 U mg(-1) for syringaldazine, from 18 to 1565 U mg(-1) for ABTS, and from 4 to 44 U mg(-1) for guaiacol. The apparent affinity constants (KM) also showed significant differences between the different strains, from 12 to 52 micromol l(-1) for syringaldazine, from 8 to 79 micromol l(-1) for ABTS, and from 0.46 to 6.61 mmol l(-1) for guaiacol. No differences were found either on the effect of increasing concentrations of organic solvent (acetonitrile) or on the activity pH profile. The temperature profile was the same for all the P. ostreatus strains, except for the IE8 strain, which seems to be more sensitive to temperature. The kinetic and stability data from the six P. ostreatus strains were also compared with those obtained from other white rot fungi, Coriolopsis gallica and Trametes versicolor, showing clear differences. CONCLUSION: The different P. ostreatus isolates showed different kinetic constants. SIGNIFICANCE AND IMPACT OF THE STUDY: The different enzymatic properties of laccases from various P. ostreatus strains should be considered for a potential industrial or environmental application.

Acetonitriles↗

PubMed1999

Laparoscopic choledochoduodenostomy.

Laparoscopic cholecystectomy is nowadays a well-established procedure in the management of gallbladder lithiasis. The sutures used in the past only for open surgery are progressively being introduced to laparoscopic procedures. The authors describe 25 cases of choledochoduodenostomy using the laparoscopic route. In 19 patients with choledocholithiasis and a common bile duct of > or = 2 cm, and in 6 cases of obstructive jaundice secondary to advanced unresectable pancreatic neoplasms, the technique produced good results as a permanent solution to the life-threatening problem of common bile duct obstruction. Manual anastomosis and intracorporeal knotting were easily performed and proved to be a safe technique in such cases.

Adult↗

PubMed1999

Polycyclic aromatic hydrocarbon metabolism by white rot fungi and oxidation by Coriolopsis gallica UAMH 8260 laccase.

We studied the metabolism of polycyclic aromatic hydrocarbons (PAHs) by using white rot fungi previously identified as organisms that metabolize polychlorinated biphenyls. Bran flakes medium, which has been shown to support production of high levels of laccase and manganese peroxidase, was used as the growth medium. Ten fungi grown for 5 days in this medium in the presence of anthracene, pyrene, or phenanthrene, each at a concentration of 5 microg/ml could metabolize these PAHs. We studied the oxidation of 10 PAHs by using laccase purified from Coriolopsis gallica. The reaction mixtures contained 20 microM PAH, 15% acetonitrile in 60 mM phosphate buffer (pH 6), 1 mM 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS), and 5 U of laccase. Laccase exhibited 91% of its maximum activity in the absence of acetonitrile. The following seven PAHs were oxidized by laccase: benzo[a]pyrene, 9-methylanthracene, 2-methylanthracene, anthracene, biphenylene, acenaphthene, and phenanthrene. There was no clear relationship between the ionization potential of the substrate and the first-order rate constant (k) for substrate loss in vitro in the presence of ABTS. The effects of mediating substrates were examined further by using anthracene as the substrate. Hydroxybenzotriazole (HBT) (1 mM) supported approximately one-half the anthracene oxidation rate (k = 2.4 h(-1)) that ABTS (1 mM) supported (k = 5.2 h(-1)), but 1 mM HBT plus 1 mM ABTS increased the oxidation rate ninefold compared with the oxidation rate in the presence of ABTS, to 45 h(-1). Laccase purified from Pleurotus ostreatus had an activity similar to that of C. gallica laccase with HBT alone, with ABTS alone, and with 1 mM HBT plus 1 mM ABTS. Mass spectra of products obtained from oxidation of anthracene and acenaphthene revealed that the dione derivatives of these compounds were present.

Anthracenes↗

PubMed1996

Biochemical method for chlorine dioxide determination.

Chlorine dioxide is a disinfectant used worldwide. In this article, a new enzymatic method for the determination of chlorine dioxide has been developed. This rapid spectophotometric assay is able to detect from 0.2 to 4 mg/liter of chlorine dioxide. The method is based on the capacity of horseradish peroxidase to decolorize reactive yellow 17 in the presence of chlorine dioxide. The effects of several compounds on the assay have been determined. Except sodium hypochlorite, no interference was detected with 18 compounds including chlorides, sulfates, carbohydrates, amino acids, proteins, and organics. The biochemical method is faster and easier than the previous volumetric, amperometric, and colorimetric methods which are laborious and time-consuming.

Chemistry Techniques, Analytical↗

PubMed1985

Isolation of three new avian sarcoma viruses: ASV 9, ASV 17, and ASV 25.

The newly isolated avian sarcoma viruses, ASV 9, 17, and 25, cause fibrosarcomas in young chickens and induce foci of transformed cells in chick embryo fibroblast cultures. They are defective in replication and belong to envelope subgroup A. The sizes of their genomes are 6 kb (ASV 9), 5 kb (ASV 17), and 6 kb (ASV 25), respectively. All three contain long terminal repeat (LTR) and gag sequences but lack pol. env is absent from ASV 9 and ASV 25, but some env sequences are detectable in ASV 17. None of the defective viral genomes hybridized to selected onc probes representing src, fps, yes, myc, myb, and erb A. erb B appears absent from ASV 9 and ASV 17, but some hybridization between the erb B probe and the RNA of ASV 25 was detected. ASV 9 codes for a transformation-specific gag-linked protein of 130kDa. Multiple gag-linked transformation-specific proteins are seen in ASV 17 and 25; they require further study.

Animals↗

PubMed1984

Characteristics of three new avian sarcoma viruses, ASV 9, ASV 17, and ASV 25.

Three new avian sarcoma viruses, ASV 9, ASV 17, and ASV 25, were isolated from spontaneous tumors. They transform chicken embryo fibroblasts but not hemopoietic cells and induce fibrosarcomas in young chicks. All three viruses belong to the envelope subgroup A and cannot replicate without a helper virus, because they lack the pol and most, if not all, of the env gene. ASV 9 and ASV 17 have a genome of 5.0 kb; the genome of ASV 25 is 6.0 kb. The following onc sequences were tested for homology to the genomes of the three new avian sarcoma viruses: src, fps, yes, myc, myb, erbA, and erbB. These tests were negative except for erbB which showed faint hybridization with the genome of ASV 25. ASV 9 codes for a prominent 130-kdalton gag-linked transformation-specific protein. ASV 17 and ASV 25 transformed cells appear to contain multiple gag-linked transformation-specific proteins that still require further study.

Animals↗

PubMedDate not supplied

Enzyme conjugation to the polysaccharide chitosan: smart biocatalysts and biocatalytic hydrogels.

Laccase from Coriolopsis gallica was conjugated to the renewable biopolymer chitosan using carbodiimide chemistry. The laccase-chitosan conjugate was observed to offer three unique properties. First, the laccase-chitosan conjugate displayed pH-responsive behavior such that the conjugate was soluble and active under acidic conditions, but precipitated when the pH was raised toward neutrality. Second, the laccase-chitosan conjugate was more stable than free laccase at extreme pHs. At pH 1, the inactivation rate constant (k(in)) for the soluble laccase-chitosan conjugate was 20-fold less than that for free laccase. At pH 13, k(in) for the insoluble laccase-chitosan conjugate was nearly 3-fold less than that for free laccase. Finally, the laccase-chitosan conjugate could be cross-linked under mild conditions to create biocatalytic hydrogels. Potential benefits for enzyme-chitosan conjugates are discussed.

Biopolymers↗

PubMedDate not supplied

Paraquat poisoning in southern Mexico: a report of 25 cases.

Paraquat is a bipyridyl herbicide used world-wide. Although accidental and deliberate ingestions of lethal doses have been reported from many countries, no case has ever been described in Mexico. The authors report on 25 cases of Paraquat poisoning in the state of Chiapas, Mexico, that occurred between 1988 and 1990. Eighty percent of the cases were men, and 64% of the cases died. Alcohol intoxication or suicidal intent were factors at the time of Paraquat ingestion in 75% of the cases. The majority of cases had learned to use Paraquat from a friend; none had been instructed by a professional. Eighty percent of cases did not know the dilution for the proper use of the herbicide, and none kept the herbicide in its original container. Attention to the law, redesign of the Paraquat packaging, and educational efforts directed at populations at risk might reduce the occurrence of poisoning in this region.

Female↗