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.     

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.     

Role for the Vacuolar H+-ATPase in Regulating the Cytoplasmic pH: An in Vivo Study Carried out in chl1, an Arabidopsis thaliana Mutant Impaired in NO-3 Transport

The effects of the growth in a medium containing NH₄NO₃ as nitrogensource were studied on cell sap pH, cytoplasmic pH and malatecontent in chl1, an Arabidopsis thaliana mutant impaired inchlorate and nitrate transport. In all the conditions testedthe pH of the cytoplasm in chl1 was more alkaline, and thatof the vacuole was more acidic as compared with those measuredin wt. Treatment with bafilomycin A1, a specific inhibitor ofthe vacuolar H⁺-ATPase, induced a small alkalinization of thevacuole, and a significant acidification of the cytoplasm, theseeffects being greater in chl1 than in wt. The greater responseof the mutant to bafilomycin Al suggests that, in the absenceof the inhibitor, the activity of the tonoplast H⁺-ATPase inchl1 is higher than in wt, this diversity being a possible reasonfor the differences in intracellular pH detected between thetwo strains. A possible role for the vacuolar H⁺-ATPase in regulatingthe cytoplasmic pH is discussed. (Received August 2, 1995; Accepted February 1, 1996)     

Insertion mutations at the maizeOpaque2 locus induced by transposable element familiesAc, En/Spm andBg

Eight independently isolated unstable alleles of theOpaque2 (O2) locus were analysed genetically and at the DNA level. The whole series of mutations was isolated from a maize strain carrying a wild-typeO2 allele and the transposable elementActivator (Ac) at thewx-m7 allele. Previous work with another unstable allele of the same series has shown that it was indeed caused by the insertion of anAc element. Unexpectedly, the remaining eight mutations were not caused by the designatedAc element, but by other insertions that are structurally similar or identical to one of two different autonomous transposable elements. Six mutations were caused by the insertion of a transposable element of theEnhancer/Suppressor-Mutator (En/Spm) family. Two mutations were the result of the insertion of a transposable element of theBergamo (Bg) family. Genetic tests carried out with plants carrying the unstable mutations demonstrated that all were caused by the insertion of an autonomous transposable element.     

Constitutive expression of FosB and its short form, FosB/SF, induces malignant cell transformation in rat-1A cells

We have established Rat-1A cell lines constitutively expressing c-Fos and the two products of the fosB gene, FosB and its short form, FosB/SF. The expressed proteins in the different stable transfectants have been characterized by immunofluorescence and immunoprecipitation analysis. Our results demonstrate that constitutive expression of FosB, like the constitutive expression of c-Fos and, to a lesser extent, FosB/SF, results in cells that grow to increased saturation densities and have the ability to grow in an anchorage-independent manner. Most important is the finding that expression of these proteins augments the tumorigenic potential of Rat-1A cells. These results show that both forms of FosB have a stimulatory effect on cell proliferation.     

DNA repair investigations in nine Italian patients affected by trichothiodystrophy.

Trichothiodystrophy (TTD) is a rare autosomal recessive disorder characterized by brittle hair, mental and growth retardation, peculiar face, ichthyosis, and in 20% of the reported cases photosensitivity. Cellular photosensitivity due to the same genetic defect present in xeroderma pigmentosum group D (XP-D) has been described in several patients. Nine patients with clinical symptoms diagnostic for TTD have been identified in Italy to date. We report the results of DNA repair investigations performed in cultured fibroblasts from these patients and 8 TTD parents. Survival, DNA repair synthesis and RNA synthesis following UV irradiation were all normal in the 8 TTD heterozygous cell strains. Among the 9 TTD-affected individuals, normal cellular UV sensitivity was observed in the 2 patients without signs of clinical photosensitivity. In contrast, the other 7 TTD cell strains showed a notable reduction in UV-induced DNA repair synthesis (UDS) levels, ranging between 40% and 5-15% of normal values. Complementation analysis indicated that in the repair-deficient TTD cell strains the genetic defect is the same as that present in XP-D cells. The biochemical heterogeneity of the XP-D defect in TTD patients characterized by different degrees of defective UDS results in different patterns of response to the killing effect of UV light in non-proliferating cells.