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Biomedical subjects

C Avila

Publications and source records attributed to C Avila.

At least 109 records · Page 6Linked to original sources
PubMed1989

Interaction between digoxin and propafenone.

The pharmacokinetic and pharmacodynamic interactions between digoxin and propafenone were investigated in 10 hospitalized patients with heart disease and cardiac arrhythmias. During steady state (0.25 mg/day) the glycoside was combined with 600 mg of propafenone daily for 1 week. The mean +/- SD serum digoxin concentration (SDC) was 0.97 +/- 0.29 ng/ml before and 1.54 +/- 0.65 ng/ml (p less than 0.003) during propafenone administration. Propafenone induced a mean decrease in 31.1 and 31.7% in total and renal digoxin clearances, respectively. The increase in SDCs was accompanied by a decrease in heart rate (HR) and shortening of QTC (QT interval corrected for HR). In patients receiving digoxin and propafenone simultaneously, the SDCs should be monitored and the digoxin dose reduced if there is evidence of toxicity.

Adult↗
PubMed1989

[Asymptomatic common truncus arteriosus in a 25-year-old patient with paroxysmal tachycardia and truncal valve insufficiency].

We present an adult patient (25-years old), free of symptoms with a congenital heart disease very infrequent and survival to adulthood is exceptional, the truncus arteriosus. Who entered to the Emergency Care Unit because of paroxysmal tachycardia. We describe the case with special reference to echocardiographic findings and we detached the rarity of this congenital heart disease in adulthood.

Adult↗
PubMed1989

[The development of the anti-phospholipase A2 antibody response in horses inoculated with venom for the production of polyvalent antisnake serum in Costa Rica].

The development of antibody response against phospholipase A2 activity of Bothrops asper venom was studied in a group of adult and healthy horses used in the production of the polyvalent antivenom at the Instituto Clodomiro Picado. Simultaneously, the general condition of the animals during the immunization schedule was also studied. There was a great individual variability in the immune response, although most of the horses studied reached the highest neutralizing titer after injection of doses of venom of 30 mg and 50 mg. On the other hand, in horses that had been previously immunized and were infected for a second immunization, the highest antibody titer was observed 16-22 days after inoculation. There were only mild alterations in the general condition of the horses as a consequence of venom inoculation. However, local abscesses, fistulae and fibrosis were observed at the site of venom injection. On the basis of the conspicuous individual variability observed, it is proposed that the immune response in horses used in the production of antivenom must be evaluated on individual basis, instead of working with pools of serum samples.

Animals↗
PubMed1988

Colorectal cancer. The bases for a comprehensive follow-up.

The purpose of this article was to review the effectiveness of follow-up in patients with colorectal cancer submitted to curative treatment. A comprehensive follow-up involves rational initial management of the primary tumor, knowledge of prognostic factors, selection of the patient to be followed, determination of the time for follow-up, use of the most appropriate tests for early diagnosis of recurrence, and eventual curative treatment. The updated answers to all these questions are given through an extensive review of the world literature and confronted with the authors' experience of eight years of follow-up in a series of 170 colorectal cancer patients treated for cure. Although the future might be more promising, past world experience suggests only a few patients could be saved. It is concluded that there is no place for incomplete and disperse screening tests, and only comprehensive, intensive, and very well-coordinated follow-up programs should be undertaken if better results are hoped to be achieved.

Colonic Neoplasms↗
PubMed1988

An alternative in vitro method for testing the potency of the polyvalent antivenom produced in Costa Rica.

The ability of several batches of polyvalent antivenom to neutralize indirect hemolytic activity of Bothrops asper venom was studied using a sensitive plate test. All samples of antivenom tested effectively neutralized this activity. A highly significant correlation was observed between neutralization of indirect hemolysis and neutralization of lethal activity. This simple and sensitive in vitro test could be used to monitor antibody levels in horses immunized to produce polyvalent antivenom.

Animals↗
PubMed1988

Production of monovalent anti-Bothrops asper antivenom: development of immune response in horses and neutralizing ability.

A monovalent antivenom was produced by immunizing two horses with venom of the pit viper Bothrops asper (Ophidia: Viperidae). Although development of the immune response against four toxic and enzymatic activities of the venom was similar in both horses during the first two thirds of the immunization schedule, antibody response in one of the horses reached much higher levels in the last part of the immunization. Immunoelectrophoretic analysis indicates that there were precipitating antibodies in the sera of these horses during all the stages of immunization. However, immunoprecipitation did not correlate with the ability of sera to neutralize toxic activities of B. asper venom. Monovalent antivenom was more effective than the commercially available polyvalent antivenom in the neutralization of Bothrops asper venom. On the other hand, despite the fact that it neutralizes lethal and hemorrhagic activities of the venoms of Lachesia muta and Crotalus durissus durissus, it was less effective than polyvalent antivenom in these neutralizations. Moreover, it does not neutralize defibrinating activity induced by these two venoms, whereas it neutralizes this effect in the case of B. asper venom. It is proposed that monovalent antivenom may be highly effective in the case of envenomations induced by Bothrops asper venom; its use in treating accidents by L. muta and C. durissus would be indicated only if polyvalent antivenom is not available. Results also demonstrate that it is important to monitor antibody response individually in horses being immunized for antivenom production, due to the conspicuous variability in the response of different animals.

Animals↗
PubMed1987

Different Characteristics of the Two Glutamate Synthases in the Green Leaves of Lycopersicon esculentum.

The two glutamate synthases, NAD(P)H- and ferredoxin-dependent, from the green leaves of tomato plants (Lycopersicon esculentum L. cv Hellfrucht frühstamm) differed in their chemical properties and catalytic behavior. Gel filtration of NAD(P)H enzyme gave an apparent molecular size of 158 kilodalton, whereas the ferredoxin enzyme molecular size was 141 kilodalton. Arrhenius plots of the activities of the two enzymes showed that the NAD(P)H enzyme had two activation energies; 109.6 and 70.5 kilojoule per mole; the transition temperature was 22 degrees C. The ferredoxin enzyme however, had only one activation energy; 56.1 kilojoule per mole. The respective catalytic activity pH optima for the NAD(P)H- dependent and the ferredoxin dependent enzymes were around 7.3 and 7.8. In experiments to evaluate the effects of modulators aspartate enhanced the NAD(P)H-linked activity, with a K(a) value of 0.25 millimolar, but strongly inhibited that of the ferredoxin-dependent glutamate synthase with a K(i) of 0.1 millimolar. 3-Phosphoserine was another inhibitor of the ferredoxin dependent enzyme with a K(i) value of 4.9 millimolar. 3-Phosphoglyceric acid was a potent inhibitor of the ferredoxin-dependent form, but hardly affected the NAD(P)H-dependent enzyme. The results are discussed and interpreted to propose different specific functions that these activities may have within the leaf tissue cell.

Journal Article↗
PubMed1986

Immunochemical comparison of glutamine synthetases from some solanaceae plants.

The presence of different glutamine synthetase isoenzymes in different Solanaceae plants and their relative antigenicities against antiglutamine synthetase from tomato leaf serum were studied. All the plants tested showed one glutamine synthetase isoenzyme except for Mandragora autumnalis, which showed two, after discontinuous polyacrylamide gel electrophoresis and specific in situ assay. Antigenicities were compared by the double immunodiffusion technique. The Nicotiana glauca enzyme showed equal reactivity to that of Lycopersicon esculentum, but its antigenicity was higher than Withania frutescens, Datura stramonium, and Hyoscyamus niger. The study of relative antigenicities permitted differentiation of the glutamine synthetase enzymes from uncultivated species of Solanaceae.

Journal Article↗
PubMed1984

Separation of two forms of glutamate synthase in leaves of tomato (Lycopersicon esculentum).

Two forms of glutamate synthase, one dependent on NAD(P)H, and the other on ferredoxin, have been completely separated by ionic exchange chromatography on DEAE cellulose. The NAD(P)H dependent enzyme was further purified by affinity chromatography with Blue Sepharose, showing Km values of 0.5 mM, 0.3 mM and 1.7 microM for glutamine, 2-oxoglutarate and NADH, respectively. Ferredoxin dependent enzyme was also purified to electrophoretic homogeneity; the Km values were 0.5 mM, 0.2 mM and 0.2 microM for glutamine, 2-oxoglutarate and ferredoxin, respectively. These results support the glutamine synthetase - glutamate synthase pathway for nitrogen assimilation.

Ferredoxins↗
PubMed1982

Pituitary response to luteinizing hormone-releasing hormone analog at sea level and high altitudes.

Two groups of subjects living at different altitudes were stimulated with synthetic luteinizing hormone-releasing hormone (LH-RH) or with an LH-RH analog. One hundred micrograms LH-RH was given subcutaneously to 19 men and 19 women, all normal, of reproductive age, and living at sea level, and to 19 men and 20 women living at a high altitude (2940 m). In neither sex, however, were the differences in peak responses for both gonadotropins significantly different between the sea level and high-altitude groups. Plasma levels of LH and follicle-stimulating hormone (FSH) were also measured after administration of [D-Leu6, des Gly-NH2(10)]-LH-RH ethylamide (25 micrograms subcutaneously) in 32 men and 37 women living at sea level and at high altitude. The analog induced a powerful and protracted stimulation of the release of LH and FSH irrespective of altitude and sex. The responses of men and women to the LH-RH analog, both for LH as well as for FSH, were significantly greater at sea level than at high altitudes.

Adolescent↗