1H- and13C-NMR spectroscopic studies of lipid extracts of the red algaGracilaria longa

Lipid extracts of the red algaGracilaria longa were studied by¹H- and¹³C-NMR spectroscopy. Peaks in the¹³C-NMR spectra attributable to sterols, chlorophylls and carotenoids allowed free and acylated cholesterol, chlorophylla and lutein to be identified as the most abundant components of these classes. A content of 0.5 ± 0.1 μmoles of total cholesterol/g wet alga was estimated from the¹H-NMR spectrum, which also allowed the determination of the phosphatidylcholine/total lipid molar ratio (9.5 ± 0.5%). The¹³C-NMR spectroscopic experiments provided information on the position of the double bonds on the fatty acid residues. A comparison between NMR spectra of lipid extracts obtained for wet and dried alga showed that the alga undergoes both a dramatic peroxidation and some glycolipid degradation during the drying process.     

CD4+ T cell response to the human acetylcholine receptor alpha subunit in myasthenia gravis. A study with synthetic peptides

The production of antinicotinic acetylcholine receptor (AcChR) antibodies in myasthenia gravis (MG) is modulated by specific Th (CD4+) lymphocytes that can recognize epitopes on the denatured AcChR alpha subunit. Thirty-two overlapping synthetic peptides corresponding to the complete sequence of human AcChR alpha subunit were used to investigate the anti-alpha subunit response of unselected lymphocytes and of CD8(+)-depleted, CD4(+)-enriched lymphocytes from the blood of nine MG patients and from four healthy controls. One subject was a newly diagnosed MG patient that was tested three times after the development of the disease. An anti-AcChR response of the CD4(+)-enriched cells was present that could be detected only after removal of the CD8+ population and that seems to be related to the clinical conditions of the patient. The high basal rate of the cell proliferation of the unselected unstimulated blood lymphocytes and the normal basal rate observed for the CD8(+)-depleted population suggested the presence of activated CD8+ cells. The study of surface markers of the T cells confirmed the existence of activated CD8+ and CD4+ cells in numbers correlated with the severity of the disease and the results of the in vitro response of the T cells. The anti-AcChR activity of the CD4+ cells in MG may be a useful marker of the activity of the disease and it seems to be influenced by activated CD8+ cells present in the patients' blood.     

Analysis of Chlamydomonas reinhardtii histones and chromatin

Chromatin spreads made from isolated nuclei of the unicellular green alga Chlamydomonas reinhardtii show the beaded fibers typical of eukaryotic polynucleosomes. Micrococcal nuclease digestions confirmed the presence of nucleosomes with a repeat length of 189 base pairs, essentially the same as typical mammalian cells. Basic nuclear proteins extracted from isolated nuclei or chromatin with 1 M calcium chloride and 0.3 M hydrochloric acid are resolved into seven major components by electrophoresis in the presence of sodium dodecyl sulfate (SDS). These seven components were subjected to qualitative peptide mapping with V8 protease on SDS gels for comparison with the major histone components of calf thymus. Finally, the C. reinhardtii basic nuclear proteins were fractionated by reversed phase high performance liquid chromatography and their amino acid composition determined. From these studies, we conclude that C. reinhardtii has a full complement of the five histones with properties very similar to those of both higher animals and higher plants.