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Biomedical subjects

M Miranda

Publications and source records attributed to M Miranda.

At least 145 records · Page 8Linked to original sources
PubMed1987

A study on the in vitro interaction between tyrosinase and glutathione S-transferase.

The actions of glutathione S-transferase and tyrosinase on the in vitro production of glutathionyl-3,4-dihydroxyphenylalanine and the dopachrome level in the presence of GSH and L-3,4-dihydroxyphenylalanine were studied. No clear evidence of complementarity between tyrosinase and glutathione S-transferase was observed; on the contrary, in the presence of glutathione S-transferase the glutathionyl-3,4-dihydroxyphenylalanine yield was lower than with tyrosinase only, as measured by HPLC. It is concluded that the spontaneous conjugation of GSH with dopaquinone should probably be high enough to scavenge the toxic quinone and to produce precursors for phaeomelanogenesis.

Animals↗
PubMed1987

Glutathione transferase activity during Bufo bufo development.

High levels of glutathione transferase activity were measured during the development of the embryos of Bufo bufo including unfertilized eggs. After stage 4 glutathione transferase activity gradually decreased until stage 25 when the minimum was reached. No change in the number of isozymes was noted during development according to isoelectric focusing analysis performed on the cytosolic fractions of selected stages.

Animals↗
PubMed1987

Restriction patterns of model DNA treated with 5,6-dihydroxyindole, a potent cytotoxic intermediate of melanin synthesis: effect of u.v. irradiation.

The interaction of 5,6-dihydroxyindole, a putative cytotoxic intermediate of melanin synthesis, with model lambda phage DNA has been investigated by using type II restriction endonucleases and CsCl buoyant density centrifugation. As evidenced by agarose gel electrophoresis and density gradient profiles, the 5,6-dihydroxyindole or u.v. treated DNAs, restricted or not, are modified. U.v. irradiation enhances 5,6-dihydroxyindole binding to DNA, but no sequence specific binding was observed. The action of L-3,4-dihydroxyphenylalanine on the restriction patterns of lambda phage DNA was also investigated and the effect appeared smaller, by qualitative evaluation, than that produced by 5,6-dihydroxyindole.

Bacteriophage lambda↗
PubMed1986

Glutathione peroxidases and glutathione reductase activities during Bufo bufo development.

Glutathione peroxidases and glutathione reductase activities are expressed from the early stage of Bufo bufo development. Selenium-dependent and selenium-independent glutathione peroxidase activities fluctuated independently. The activity of selenium-independent was found to be higher than that of selenium-dependent glutathione peroxidase through all stages of development. Glutathione reductase activity, after a slight fall from stage 4 to stage 7, constantly increased up to stage 25.

Animals↗
PubMed1985

5,6-Dihydroxyindole oxidation by mammalian, mushroom and amphibian tyrosinase preparations.

The oxidation of 5,6-dihydroxyindole by tyrosinases from mushroom, Harding-Passey melanoma, bovine eye and Bufo bufo embryo has been investigated. The apparent Km values for this substrate were measured and found to be of the same order of magnitude as those for L-tyrosine and L-3,4-dihydroxyphenylalanine, as reported in the literature (5 x 10(-4) M). The 5,6-dihydroxyindole oxidases of mushroom and T4 melanoma isozyme are sensitive to phenylthiourea, while, on the other hand, those from crude preparations of bovine and B. bufo tyrosinases are not sensitive to the inhibitor in an evident manner. The action of some indole derivatives on the 5,6-dihydroxyindole oxidase of mushroom has also been investigated.

Animals↗
PubMed1985

Abnormalities of interdigestive motility complex and increased duodenogastric reflux in gastric ulcer patients.

Just as cyclic changes in motility and secretions occur during fasting, recent evidence demonstrates that duodenogastric reflux during fasting is also cyclic and related to the motility and secretory variations. We investigated the characteristics of the migrating motility complex and duodenogastric reflux in 17 patients with gastric ulcer and compared these characteristics to those of 16 healthy subjects. We found three abnormalities of the complex in patients with gastric ulcer: (1) the antral motility was significantly decreased during the phase II of the complex (P less than 0.05) when compared to controls; (2) in about two thirds of them, the phase III of the complex was initiated at the duodenum or more distally; and (3) the mean bile salt concentration in the gastric aspirate was significantly higher (P less than 0.05) than that of the controls. We observed no relationship between the ulcer activity, the location of the crater, and the motility or reflux abnormalities.

Adolescent↗
PubMed1984

Possible genotoxicity of melanin synthesis intermediates: tyrosinase reaction products interact with DNA in vitro.

The actual cellular target of the cytotoxic intermediates of melanin synthesis is not yet known. In the present paper it is shown that eukaryotic DNA binds in vitro to soluble reaction products of tyrosinase (EC 1.14.18.1) and is physically modified, as ascertained by the following criteria: (a) buoyant density in cesium chloride density gradients; (b) polyacrylamide gel electrophoresis; (c) deoxyribonuclease (EC 3.1.4.5) test; (d) electron microscopy. The results reported here support the view that DNA itself may be a target for the cytotoxic intermediates of melanin synthesis.

Animals↗
PubMed1984

Comparative effect of gastrin on hydrogen ion secretion, antroduodenal motility and the interdigestive motility complex (IDMC) in man.

The physiological role of gastrin in H+ secretion is well established. We decided to study the effects of physiological doses of gastrin (as evidenced by H+ secretion and postprandial serum gastrin levels) on antroduodenal motility in order to delineate its role in antral motility regulation. Nine healthy male subjects, mean age 31 years, had two studies on different days. On day 1, gastroduodenal motility was monitored with a continuously perfused catheter system while gastric secretions were aspirated. After a basal period of 45 min, human synthetic gastrin (hG-17) was infused intravenously in consecutive doses of 6.25, 25, 100, and 400 pmol/kg/hr during 45 min each. On day 2, all subjects had a standard protein meal. Blood was withdrawn on both days for gastrin measurement by RIA. Increasing amounts of hG-17 caused a stepwise increase in serum gastrin and acid output. The D50 for H+ secretion was 25 pmol/kg/hr hG-17. The mean postprandial gastrin level was 31 +/- 5 pM, a level which was comparable to that seen during infusion of hG-17 6.25 pmol/kg/hr. At these serum gastrin levels, antral motility was either reduced or unchanged. Duodenal motility was unchanged. A reduction in the antroduodenal motility ratio was seen at these levels, but there was no interruption of the interdigestive motility complex. These results suggest that at physiological levels, gastrin by itself does not seem to have a major role in human antroduodenal motility regulation.

Adult↗
PubMed1984

Tyrosinase-like activity in normal human substantia nigra.

A tyrosinase-like activity was found in human substantia nigra by polyacrylamide gel electrophoresis of fractions prepared from homogenates of the substantia nigra. The enzyme activity was detected by staining the gels with L-3,4-dihydroxyphenylalanine, dopamine and 5,6-dihydroxyindole as substrates for tyrosinase (EC 1.14.18.1). A case of parkinsonism does not show the L-3,4-dihydroxyphenylalanine and dopamine oxidase activities.

Aged↗
PubMed1984

[Myasthenia and Basedow's hyperthyroidism].

The authors report an exceptional case of myasthenia gravis associated with Graves' disease. Myasthenia gravis appeared at age 8 years. Hyperthyroidism was diagnosed at age 12 1/2 and quickly worsened, with signs of cardiothyrotoxicosis. In addition to the diagnostic difficulties, the immunologic origin seems to be implicated in these diseases. Thymectomy associated with subtotal thyroidectomy was performed, with good results during an 18 months follow-up.

Child↗
PubMed1983

Electrophysiologic findings in long-term asymptomatic chagasic individuals.

Under electrophysiologic studies, 44 asymptomatic chagasic individuals were studied. The mean age was 39.9 years, with 26 being male. The surface ECG showed normal tracings in 12 patients, left anterior fascicular block in three, incomplete right bundle branch block in two, and right bundle branch block in 27 (isolated in six, associated with left anterior fascicular block in 19 and with left posterior fascicular block in two). Sinus nodal dysfunction was found in eight (18.1%), and 29 (66%) presented with some form of abnormal AV nodal behavior during atrial stimulation. Repetitive ventricular beats were recorded in 17 (41.4%) patients. Finally, in 19 (43.1%), patterns of dysfunction at two or more levels of the cardiac conducting system were found. It is concluded that the chagasic cardiomyopathy produces diffuse lesions in the conducting tissue of the human heart in the stages when the disease is detected, and that the individuals are still asymptomatic.

Adult↗