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Biomedical subjects

A Ayala

Publications and source records attributed to A Ayala.

283 records · Page 16Linked to original sources
PubMedDate not supplied

Relationship between enzymatic activity loss and post-translational protein modification in aging.

During aging, there is a decrease in the activity of many enzymes. The mechanism causing the loss of activity is still not well understood in most cases. We have studied the decrease in the activities of the malic, 6-phosphogluconate dehydrogenase and superoxide dismutase enzymes. The old malic enzyme is about 36% less active than the young enzyme and the old 6-phosphogluconic dehydrogenase enzyme is about 26% less active than the young enzyme. In this paper, some chemical properties of these enzymes are studied. Diethyl pyrocarbonate measurements indicate that the old malic enzyme has 1 histidine residue less than the young malic enzyme. Moreover, the treatment of the young malic enzyme with ascorbate for 15 min produces the loss of 36% of enzymatic activity and the loss of 1.2 histidine residues. 2,4,6-trinitrobenzenesulfonic acid measurements indicate that the old 6-phosphogluconate dehydrogenase enzyme has 11 lysine residues less than the young 6-phosphogluconate dehydrogenase enzyme. The proteolysis with trypsin produces more peptides in the young 6-phosphogluconate dehydrogenase enzyme than in the old one. However, similar numbers of peptides were produced when endoproteinase Arg-C was used in both enzymes, young and old 6-phosphogluconate dehydrogenase. Moreover, the treatment of young 6-phosphogluconate dehydrogenase enzyme with ascorbate for 15 min produces the loss of 8 lysine residues. These results suggest that during aging the modification of histidine residue could be involved in the loss of malic enzyme activity, and the modification of lysine residues could be involved in the loss of 6-phosphogluconate dehydrogenase activity. These results could also suggest that the modification of histidine and lysine residues during aging could be produced by oxidation. This could be a general process in aging, with an increase in the oxidation of many proteins. The relevance of this process in the aging effects must be related to the kind of proteins that are susceptible of oxidation and that this oxidation affects their enzymatic or biological function. We have also studied other enzymes one of which is the superoxide dismutase enzyme involved in the protection against oxidative damage. Our results are similar to those described for malic enzyme. In the latter case, the failure to measure one of the histidines in the Cu/Zn SOD is due to a chemical modification, probably caused by oxidation of the residue.

Journal Article↗
PubMedDate not supplied

Preferential use of less toxic detoxification pathways by long-lived species.

This study was undertaken to determine whether the detoxification pathways producing the least oxidative stress appear to be favored in longer-lived mammalian species. Firstly, we focused on the cytochrome P-450 monooxygenase system. Although this system is an important component of the defenses that protect living organisms against toxic chemicals, some reactions catalyzed by the cytochrome P-450 system result in the formation of products that are highly reactive as well as active oxygen species. Our results suggest that the lower amount of hepatic cytochrome P-450 content found in longer-lived species may have evolved to reduce the toxic side-effect of this detoxification system. Support of the idea that the cytochrome P-450 system is an important source of oxidative stress is the positive correlation between cytochrome P-450 content and the amount of oxidized proteins found in liver of different human individuals. Secondly, we have measured the specific activity of other detoxification enzymes as a function of life span. Instead of a direct comparison of detoxification capabilities of the species, the approach used in this study was: (1) to select those detoxification enzymes which utilize the same substrate but differ in toxicity of the intermediate compounds formed in the reaction, and (2) to measure the levels of these enzymes in the two pathways to determine which pathway is dominant for each species. Our results suggest that the detoxification pathways producing the least oxidative stress do appear to be favored in longer-lived species.

Journal Article↗
PubMedDate not supplied

Giant-cell tumor of the tendon sheath arising from the posterior cruciate ligament of the knee: a case report and review of the literature.

The localized form of a giant-cell tumor of the tendon sheath is uncommon and rarely intraarticular. While the sonographic findings are nonspecific, the magnetic resonance (MR) findings can be diagnostic. Relatively homogeneous iso- or marginal hyperintensity on T2-weighted sequences, lack of susceptibility effects due to hemosiderin, the demonstration of a fibrous capsule and the absence of adjacent joint involvement may help to differentiate localized and diffuse forms of giant-cell tumors of tendon sheaths and pigmented villonodular synovitis.

Female↗
PubMedDate not supplied

The ultrastructure and histogenesis of male germ neoplasia with emphasis on seminoma with early carcinomatous features.

The range of ultrastructural morphology was studied in 107 male germ cell neoplasm to assess relationships among tumor subtypes and to consolidate diagnostic criteria. Eighty-three pure-pattern neoplasms including 47 seminomas, 26 embryonal carcinomas, 10 endodermal sinus tumors, and 24 mixed germ cell tumors were analyzed. In the seminoma category, 4 cases showing cell surface specialization in keeping with early carcinomatous transformation were noted. The finding suggested a closer link between seminoma and nonseminomatous germ cell tumors than had been traditionally recognized and was in keeping with other clinical, histologic, biochemical, and xenograft observations. Subtypes of nonseminomatous germ cell tumors also exhibited a continuum of ultrastructural morphology with some types such as embryonal carcinoma and endodermal sinus tumor often blending together. At a practical level, electron microscopy has been of value in selected differential diagnoses such as seminoma versus lymphoma.

Choriocarcinoma↗
PubMedDate not supplied

Dietary n-3 polyunsaturated fatty acid modulation of immune cell function before or after trauma.

We describe the role of increased eicosanoid production in inducing immunodepression associated with shock and trauma and the potential mechanisms by which prostaglandins produce immunosuppression. The effects of prefeeding with a diet high in n-3 polyunsaturated fatty acids (PUFAs) in preventing trauma-induced immunosuppression, and of such a diet on cellular immunity in patients after trauma are described. The potential mechanisms by which enteral diets containing n-3 PUFAs produce beneficial effects are also discussed. Although there is controversy concerning the immunomodulatory mechanisms of this diet, most of the information available indicates that dietary supplementation with n-3 PUFAs may prevent immunosuppression after trauma. Further studies are needed, however, to determine the precise composition and duration of supplementation with n-3 PUFAs that prevent the deleterious immune responses but do not alter normal immunoresponsiveness.

Dietary Fats↗
PubMedDate not supplied

Direct quantitative determination of peptides and proteins in PVDF transfer membrane using a computing densitometer.

In this paper we describe a method that makes it possible to quantify bands or spots directly on membranes using a computing densitometer. The method is based on the fact that polyvinylidene difluoride (PVDF) membrane is translucent when immersed in solutions containing > 50% methanol. Peptide markers (2.512-16.949 kDa), as well as purified Neuropeptide Y, have been used to optimize direct densitometry of PVDF membrane. For all peptides and proteins analyzed, the optical response of the instrument to peptide and protein bands in PVDF membrane wetted in 50% methanol was linear and highly reproducible. The method described here is useful for a rapid quantification of peptides and proteins on PVDF membrane and is an alternative to RIA, ELISA or bioassay.

Blotting, Western↗