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At least 451 records · Page 25Linked to original sources
PubMed1985

Incorporation of (35S)sulfate and (3H)glucosamine into glycoaminoglycans in rat incisor predentine and dentine: comparison by autoradiography of fixation by rapid-freezing, freeze-substitution, and aldehyde fixation.

At 4 and 24 hours after injection of (35S)sulfate, there were 22-67% fewer silver grains on conventionally fixed sections than on sections fixed by cryotechniques. Differences were smaller when (3H) glucosamine was chosen as precursor. The number of silver grains increased between 4 and 24 hours in predentine and in a 30-micron band of dentine that had already undergone mineralization. Only a few grains were observed, however, in the 5-micron dentine band located at the mineralization front. This suggests that glycoaminoglycans, which in predentine have a space-filling role, facilitate transport and diffusion and inhibit mineralization, may limit crystal growth in dentine once a certain degree of apatite formation has been reached. All these properties are correlated with the structural and functional properties of the tissues.

Aldehydes↗
PubMed2001

Differential responses of superoxide dismutase in freezing resistant Solanum curtilobum and freezing sensitive Solanum tuberosum subjected to oxidative and water stress.

In photosynthetic tissues superoxide dismutase (SOD) plays an important role by scavenging the superoxide radical whose production is an usual reaction in chloroplast thylakoids. To test the differential response of SOD, two Andean potato species differing in frost resistance, Solanum curtilobum (frost resistant) and Solanum tuberosum (frost sensitive), were subjected to methyl viologen-mediated oxidative stress and polyethylene glycol (PEG)-induced water stress. A significant increment (approximately two-fold) in total SOD and FeSOD activity, which occupied about 50% of the total activity, was found when leaves of S. curtilobum were exposed to water stress. In contrast, the SOD activity in leaves of S. tuberosum remained unchanged. The exposure of leaves of S. curtilobum to oxidative stress increased total SOD and FeSOD activity by 350%. High correlation between SOD activity and the F(v)/F(m )ratio under both PEG induced water stress and MV-mediated oxidative stress was observed. This suggests that SOD can protect PSII from superoxide generated by oxidative and water stress. The higher SOD activity could be an important mechanism to explain why some natives Andean potato like S. curtilobum are more resistant to abiotic stresses than S. tuberosum.

Journal Article↗
PubMed1999

Nuclear beta-catenin in colorectal tumors: to freeze or not to freeze? Colon Cancer Team at IMAS.

beta-Catenin mediates the interaction of E-cadherin with alpha-catenin and the actin cytoskeleton. Recent evidence indicates that when the tumor suppressor gene APC is inactivated, beta-catenin can translocate to the nucleus, where it acts as a transcriptional regulator. Because APC is inactivated in most colorectal cancers, beta-catenin nuclear localization would be expected in these tumors. In a study of adhesion molecule expression in frozen colorectal cancer tissues, we were surprised by failure to detect nuclear beta-catenin. Here we compared the reactivity of an anti-beta-catenin monoclonal antibody with 11 colorectal cancers using immunohistochemistry on sections of frozen or paraffin-embedded samples. beta-Catenin was never detected in the nuclei of normal or tumor cells in frozen tissue sections. By contrast, in 8/11 cases it was detected in the nuclei of tumor cells but not of normal cells in paraffin-embedded tissue sections. These results were confirmed with an independent rabbit polyclonal anti-beta-catenin serum. We also examined beta-catenin distribution in SW480 colon cancer cells, in which its nuclear accumulation has been reported. As in tissues, nuclear beta-catenin was detected in paraffin-embedded but not in frozen samples. These findings are relevant because of the increasing interest in the study of beta-catenin in tumors, based on its dual role in cell adhesion and transcriptional regulation.

Cell Nucleus↗