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Biomedical subjects

E Silva

Publications and source records attributed to E Silva.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Lysozyme photo-oxidation by singlet oxygen: properties of the partially inactivated enzyme.

This work studies the behaviour of partially inactivated lysozyme formed by the effect of singlet oxygen, which was obtained through the irradiation of the native enzyme solution with polychromatic visible light using Methylene Blue as a sensitizer. The polyacrylamide gel analysis of the partially inactivated lysozyme solution shows the presence of different protein fractions. One of them, which corresponds to 53% of the original enzyme, has the same migration as the native enzyme. The others are a mixture of fractions (47%) that show slower migration to the cathode. When this experiment is carried out in the presence of sodium dodecyl sulfate, only one fraction is obtained, which rules out the presence of covalently aggregated forms of lysozyme. The partially inactivated lysozyme has lost 74% of the fluorescence emission of the tryptophan (Trp) residues. By using the anionic quencher iodide, it is determined that 45 and 36% of the fluorescence emission arising from the native and partially inactivated enzyme, respectively, are due to Trp residues exposed to the solvent. Michaelis-Menten constants (K(in)) of 0.296 and 0.511 (mg/ml) and maximum initial rates (Vmax) of 0.295 and 0.190 (mg/ml min) are determined for the native and the partially inactivated enzyme solutions, respectively. The same inactivation profile is found when the denaturing effect of increasing urea concentration on both the native and partially inactivated lysozyme is studied. It is postulated that the partially inactivated lysozyme solution is composed of one protein fraction with enzymatic activity similar to that of the native enzyme and also of a mixture of fractions (47% of the total enzyme) with very low activity and characterized by a high tryptophan photo-oxidation.

Kinetics↗
PubMedDate not supplied

Immediate and delayed hypersensitivity to mite antigens in atopic dermatitis.

Atopic dermatitis (AD) is a common disorder and appears to be on the increase, especially among children. It was thought at first to be a manifestation of immediate hypersensitivity, but it is now known that delayed hypersensitivity also plays an important role. Sensitivity to mite antigens is found in 20% to 60% of patients when immediate hypersensitivity is evaluated by the detection of specific IgE antibodies and prick tests, and in 30% to 50% of patients when delayed hypersensitivity is studied by patch testing. A prospective randomized study was carried out in the pediatric dermatology clinic on a sample of 51 children under 15 years of age. A prevalence of immediate and delayed hypersensitivity to mites, like that described for other populations, was found. It was further found that there was a positive association, not described in the literature, between the younger age groups and delayed hypersensitivity to mite antigens, while the opposite was true for immediate hypersensitivity. We believe that patch tests with airborne allergens, specifically mites, should be part of the protocol for assessing children with AD, particularly in the younger age groups.

Age of Onset↗
PubMedDate not supplied

Development and strategies of the Colombian vaccination program.

Experience in Colombia demonstrates that short-term dramatic increases in coverage can be obtained through campaigns, but these gains can only be sustained through the improvement of routine immunization services. "Channeling" of immunization-eligible infants and children to facilities has been shown to be effective, but its long-term impact is dependent on substantial, and continuing, community participation.

Colombia↗
PubMedDate not supplied

Neuroendocrine (Merkel cell) carcinomas of the skin: an ultrastructural study of nine cases.

Nine neuroendocrine tumors of the skin were examined by light and electron microscopy. The patients (7 males and 2 females) had an average age of 57 years. Seven tumors were located in the head and neck region. Light microscopic examination showed sheets of cells. In 4 cases, a tendency to form small groups of cells was observed. Contact with the epidermis was seen in only 2 cases. The dominant ultrastructural feature was the presence of cytoplasmic processes that contained membrane-bound granules 100-200 nm. Three tumors recurred locally, and in 7 patients, regional nodal metastases occurred. Three patients died of disseminated disease.

Aged↗