PubMed · 1037342
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M Nakao. 1976. Several problems concerning red cell membranes.. https://pubmed.ncbi.nlm.nih.gov/1037342/
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Sialic acids from the erythrocyte (RBC) membrane of a patient suffering from polycythemia vera, a malignant orphan disorder of hematopoietic cells, was studied using GC/MS. We found that the sialic acid diversity of these membranes was drastically reduced since only four entities were identified: Neu5Ac (91.5%) and its 1,7 lactone Neu5Ac1,7L (7.5%) which is absent in normal RBC, Neu4,5Ac(2) (0.50%) and Neu4,5Ac(2) 9Lt (0.50%); in normal RBC, Neu5,7Ac(2), Neu5,9Ac(2), Neu5Ac9Lt, Neu5Ac8S and Neu, as well as traces of Kdn, were also present. Neu5Gc and its O-alkylated or O-acetylated derivatives, which are considered by various authors as cancer markers, were not detected.
In this study we investigated some biological properties of flavonoids recovered in the aqueous (AqE) and ether (EtE) extracts from four Italian multifloral honeys. In particular, a cell-free assay was employed to detect direct reduction of ferricyanide, whereas an assay using intact human erythrocytes was used to measure the ability to donate electrons to a trans-plasma membrane oxidoreductase. It was found that the AqE displays greater "in vitro" ferricyanide-reducing activity than the EtE but, unlike the latter, is virtually ineffective in the cell-based assay. Uptake studies employing high-performance liquid chromatography/mass spectrometry (HPLC/MS) showed that the different results were explained by the inability of AqE components to cross the erythrocyte plasma membrane and by the excellent uptake of EtE flavonoids, which, once within the cell, donate electrons to the membrane oxidoreductase to efficiently reduce extracellular oxidants. The latter property appears to depend on the content of ether-soluble flavonoids in the starting honeys.
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