Biomedical subjects

Sara Santos

Publications and source records attributed to Sara Santos.

5 recordsLinked to original sources

PubMed2006

Glycerol-derived ester oligomers from cork suberin.

The cork suberin polyester was partially depolymerized by a methanolysis reaction catalyzed by calcium hydroxide. The methanolisate was analysed by ESI-MS/MS in the form of [M+Li](+) adduct-ions. This reaction solubilized a mixture of monomers and oligomers, including a set of glycerol-derived dimeric and trimeric esters. Four types of glycerol esters were identified: monoacylglycerols of alpha,omega-diacids, of omega-hydroxyacids and of monoacids; diglycerol diesters of alpha,omega-diacids; diacylglycerols of alpha,omega-diacids; monoacylglycerols of linear dimeric esters of alpha,omega-diacids and omega-hydroxyacids. The alpha,omega-diacids and omega-hydroxyacids found as monomer residues in the glycerol esters are the main ones found as cork suberin monomers. It is concluded that suberin is a glycerol-derived lipid of polymeric dimensions. Due to the protective and insulating role that it plays in plants, suberin should be considered together with the other known glycerolipids that build up biological membranes.

Dimerization↗

PubMed2006

Amplification of the major satellite DNA family (FA-SAT) in a cat fibrosarcoma might be related to chromosomal instability.

Most mammalian chromosomes have satellite DNA sequences located at or near the centromeres, organized in arrays of variable size and higher order structure. The implications of these specific repetitive DNA sequences and their organization for centromere function are still quite cloudy. In contrast to most mammalian species, the domestic cat seems to have the major satellite DNA family (FA-SAT) localized primarily at the telomeres and secondarily at the centromeres of the chromosomes. In the present work, we analyzed chromosome preparations from a fibrosarcoma, in comparison with nontumor cells (epithelial tissue) from the same individual, by in situ hybridization of the FA-SAT cat satellite DNA family. This repetitive sequence was found to be amplified in the cat tumor chromosomes analyzed. The amplification of these satellite DNA sequences in the cat chromosomes with variable number and appearance (marker chromosomes) is discussed and might be related to mitotic instability, which could explain the exhibition of complex patterns of chromosome aberrations detected in the fibrosarcoma analyzed.

Animals↗

PubMed2006

Linear aliphatic dimeric esters from cork suberin.

Cork suberin was partially depolymerized by methanolysis catalyzed by calcium hydroxide. Analysis by GC-MS of the methanolysate showed suberin monomers, including glycerol and long-chain alpha,omega-diacids and omega-hydroxyacids. ESI-MS analysis of the methanolysate showed, besides the aliphatic monomers, suberin oligomers, including linear dimeric esters of alpha,omega-diacids and omega-hydroxyacids. Two types of dimeric esters were identified: a alpha,omega-diacid linked to a omega-hydroxyacid and two inter-linked omega-hydroxyacids. The alpha,omega-diacids and omega-hydroxyacids found as monomer residues in the dimeric esters were mainly the C18 monomers with midchain substituents. The identification of these dimeric esters was based in their CID-MS/MS spectra and confirmed after synthesis of model compounds. The occurrence of inter-esterified long-chain monomers in suberin brings a new insight in the understanding of the polyester structure of this biopolymer.

Dimerization↗

PubMed2004

Comparative analysis (Hippotragini versus Caprini, Bovidae) of X-chromosome's constitutive heterochromatin by in situ restriction endonuclease digestion: X-chromosome constitutive heterochromatin evolution.

The Bovidae X-chromosome shows a considerable variation, in contrast to the preservative autosomal conservatism. The X-chromosome variation is mostly a consequence of the constitutive heterochromatin (CH) variation; in what respect to its amount and position. This is especially common among the non-Bovinae subfamilies and tribes. In order to characterize the X-chromosome CH in non-Bovinae species--Hippotragini and Caprini tribes--we have used restriction endonuclease digestion on fixed chromosomes and sequential C-banding. With these techniques we were able to distinguish between the two X-chromosome types (Hippotragini and Caprini) CH, in what respect to its position and molecular nature. Moreover, we define at least, six subclasses of CH in both X-chromosome types analyzed. Evolutionary considerations were draw based on the results obtained. The technology used here for the analysis of the Bovidae X-chromosome CH showed to be more evolutionary informative than the classical approaches.

Animals↗

PubMed2002

p65-NFkappaB synergizes with Notch to activate transcription by triggering cytoplasmic translocation of the nuclear receptor corepressor N-CoR.

Notch/RBP-Jkappa and nuclear factor-kappaB (NFkappaB) complexes are key mediators of the progression of many cellular events through the activation of specific target gene transcription. Independent observations have shown that activation of Notch-dependent transcription generally correlates with inhibition of differentiation. In contrast, activated NFkappaB complexes are required for progression of differentiation in several systems. Although some interactions between both pathways have been observed, the physiological significance of their connection is unclear. We have now demonstrated that the increase in p65-NFkappaB protein levels enhances Notch-mediated activation of the Hes1 promoter up to three-fold. This effect does not require NFkappaB transcriptional activity, and it is independent of the previously described interaction between Notch and p50-NFkappaB. Furthermore, we show that p65-NFkappaB can modulate subcellular localization of the transcriptional corepressor N-CoR, abrogating N-CoR mediated repression of the Hes1 promoter. In addition, p65-NFkappaB is able to upregulate not only the Hes1 but also other promoters containing SRE and AP-1 sites, which are repressed by N-CoR. Thus, we conclude that p65-NFkappaB can regulate gene expression by a general mechanism that involves cytoplasmic translocation of the transcriptional corepressor protein N-CoR.

3T3 Cells↗