Lipid composition of plasma membranes isolated from sunflower seedlings grown under water-stress

Plasma membranes were isolated by aqueous two-phase-partitioning from sunflower ( Helianthus annuus cv. Isabel) seedlings grown both under field irrigation and dryland conditions. Water-stressed plants showed a decrease in the leaf water potential and in the osmotic potential at full turgor, with the turgor pressure remaining at positive values. Dryland conditions also induced a reduction in the bulk modulus of elasticity. Plasma membranes of irrigated plants were characterized by high contents of phospholipids (68% of total lipids), free sterols (15. 7%) and glycolipids (9. 1%), mainly glycosphingolipids and steryl glycosides. Diacylglycerols, triacylglycerols and free fatty acids were also present. The major phospholipids were phosphatidylcholine and phosphatidylethanolamine with smaller amounts of phosphatidylinositol and phosphatidylglycerol. Following water stress, the plasma membranes showed a reduction of about 24 and 31% in total lipids and phospholipids, respectively. Also the amounts of glycolipids and diacylglycerols decreased significantly upon water stress. There was no change in free fatty acids, however, and triacylglycerols and free sterols increased. As a consequence, the free sterol to phospholipid molar ratio increased from 0. 4 to 0. 7 under water deficit conditions. The ratio of phosphatidylcholine to phosphatidylethanolamine increased from 1. 1 (control plants) to 1. 6 (water-stressed plants), while phosphatidic acid rose to 4% of total phospholipids. Dehydration did not result in any substantial change in the unsaturation level of the individual lipid classes, however. The results show that dryland conditions resulted in a marked alteration in the lipid composition of the sunflower leaf plasma membrane     

Monitoring airborne concentrations of sporangia ofPhytophthora infestans in relation to tomato late blight in Emilia Romagna,Italy

Late blight caused byPhytophthora infestans is one of the most important diseases of tomato crops in Emilia Romagna. In total, 7–8 chemical sprays are applied per season to control the disease without taking into account the risk of infection. An integrated warning service for the prediction of tomato late blight was set up in order to define a more rational disease control strategy. As a part of the warning service, a number of sites monitoringPh. infestans airborne sporangia was set up for a timely disease prediction in the regional tomato growing areas. The results of 3 years monitoring ofPh. infestans sporangia are presented. They suggest that concentrations of airborne sporangia rapidly increase 1–2 weeks prior the blight onset in the field.     

Cytochrome P-450 factors determining synthesis in strain D7 Saccharomyces cerevisiae. An alternative system to microsomal assay

Certain aspects of cytochrome P-450 induction were studied in a diploid strain (D7) of the yeast Saccharomyces cerevisiae in order to obtain cells containing a high level of metabolizing enzymes. The highest level of cytochrome P-450 was reached during the logarithmic growth phase in a 20%-glucose liquid medium. Yeast cells harvested in these conditions were used in the mutagenesis test with dimethyl nitrosamine (DMNA) as a positive control and with styrene (Sty). Both substances gave positive results, whereas Sty never showed any mutagenic activity in the conventional test with stationary growth phase cells and external metabolic activation. The test with cells from the logarithmic growth phase is proposed as a possible alternative to the liver-microsome assay, and its reliability is discussed.     

Nervous system ganglioside composition of normothermic and hibernating dormice (Glis glis)

The ganglioside pattern of seven different regions, olfactory bulb, forebrain cortex, midbrain (corpora quadrigemina), cerebellum, brain stem, pons and spinal cord, of nervous system of normothermic and hibernating dormice (Glis glis) were investigated by two dimensional thin layer chromatography and densitometric quantification. Up to thirty different ganglioside spots were resolved, fifteen of which belonging to alkali labile species. Alkali labile gangliosides were present in all the regions obtained from normothermic animals, and their content, expressed as percentage of total ganglioside-bound sialic acid, ranged from a minimum of 10.2% in olfactory bulb, to a maximum of 30.1% in spinal cord. The most abundant alkali labile gangliosides were O-Ac-GT1b, O-Ac-GQ1b and an unidentified one, we coded I3. Alkali labile gangliosides were practically undetectable in hibernating dormice. They could be recognized only in brain stem, 3.3% and olfactory bulb, 0.6%.     

Localization of DNA probes tightly linked to the Friedreich's ataxia locus by in situ hybridization in a case of pericentric inversion of chromosome 9

Summary The gene for Friedreich's ataxia (FA), an autosomal recessive neurodegenerative disorder, has been recently assigned to the long arm of chromosome 9. Linkage disequilibrium between FA and two diverse chromosome 9 markers, D9S5 and D9S15, has been detected in French, French-Canadian and Italian populations. Here, we report the physical localization of these loci by in situ hybridization of probes 26P and MCT112S identifying the D9S5 and D9S15 loci, respectively. Experiments performed on lymphocytes carrying a chromosome 9 pericentric inversion have allowed us to assign both the loci to band 9q21. Furthermore, in situ hybridization data and partial sequencing of the probe MCT112S indicate the presence of alphoid satellite DNA within this region. This suggests that MCT112S is more proximal to the centromere than 26P.     

Isolation and characterization of a tetrasialoganglioside from mouse brain, containing 9-O-acetyl,N-acetylneuraminic acid

A new ganglioside, containing an alkali-labile linkage, was extracted from mouse brain and purified. It represents 3.6% of total lipid-bound sialic acid in the tissue and was obtained in pure form with a yield of about 35%. It contains sphingosine, glucose, galactose, N-acetylgalactosamine and sialic acid in the molar ratio 1:1:2:1:4 and, upon exhaustive sialidase treatment gives the monosialoganglioside GM1. Partial acid hydrolysis, methylation analysis, gas-liquid chromatography-mass spectrometry and chromium trioxide oxidation studies showed its basic neutral glycosphingolipid core to be ganglio-N-tetraose-ceramide. Three of the four sialic acid residues are N-acetylneuraminic acid and one, as shown by gas-liquid chromatography-mass spectrometry, is 9-O-acetyl,N-acetylneuraminic acid, which contains the alkali labile linkage. 9-O-acetyl,N-acetylneuraminic acid is -ketosidically linked to position 8 of the N-acetylneuraminic acid residue bound to position 3 of the internal galactose. The other two N-acetylneuraminic acid residues form a disialosyl residue linked to position 3 of external galactose. The complete structure of the studied ganglioside is as follows: NeuAc2–8NeuAc2–3Galβ1–3GalNAcβ1–4(9-O-Ac-NeuAca2–8NeuAc2-1′-N-acylsphingosine, and it can be considered as a derivative of the tetrasialoganglioside GQ1b.     

N-(o-carboxybenzyl) chitosans: Novel chelating polyampholytes

The imine formed by chitosan with phthalaldehydic acid was reduced with sodium cyanoborohydride and the resulting N-(o-carboxybenzyl) chitosan (NCBC) was insolubilised with ethanol and acetone and obtained as a white, free-flowing powder, soluble in both acidic and alkaline solutions. A sample of NCBC with the following degrees of substitution: acetamido 42%±4%, N-(o-carboxybenzyl) amine 43%±3%, free amine 15%±1% and containing 16%±1% moisture, was characterised by IR and UV-Vis. spectrometry, titration and viscometry. The isoelectric point was 6·8; the pK_a values were 5·7 and 8·0. NCBC could be determined by UV-Vis. spectrophotometry in aqueous solutions at 274 nm; maximum viscosity of the solutions was observed at pH 4. Upon addition of NCBC to transition metal ion solutions (0·1–0·5 mm) chelation and insolubilisation took place immediately. The dependence of the collection percentage on pH, NCBC and metal ion concentrations was studied for nine metal ions.     

Changes in Rabbit Brain Cytosolic and Membrane-Bound Gangliosides During Prenatal Life

The present study deals with the developmental profile of cytosolic and membrane-bound gangliosides in rabbit whole brain from the 21st day of pregnancy, the time at which brain could be macroscopically recognized and handled, till birth. In this period of prenatal life the content of membrane-bound gangliosides showed a 2.5-fold increase, referred to fresh and dry brain weight and to membrane-bound protein; the content of cytosolic gangliosides reached a maximum at 21-22 days of pregnancy, and then underwent to birth a threefold diminution. The qualitative pattern of membrane-bound gangliosides, in the same period of life, was characterized by an increase of G_D1a and G_M1 (more marked for G_D1a), a decrease of G_T1a, G_T1b and G_Q1b and a constant level of G_D3 and G_D1b. At 21 days of pregnancy the most abundant gangliosides were G_T1b, and G_Q1b, followed by G_D1a and G_D1b; at birth it was G_D1a followed by G_T1b G_D1b, and G_M1 The qualitative pattern of cytosolic gangliosides closely resembled, during the entire period of prenatal life examined, that of membrane-bound gangliosides.     

Chelating,film-forming,and coagulating ability of the chitosan–glucan complex from Aspergillus niger industrial wastes

Waste mycelia of Aspergillus niger from a citric acid production plant are simply treated with boiling 30–40% NaOH aqueous solutions for 4–6 hr to obtain the insoluble chitosan-glucan complex whose infrared, ESR, and x-ray diffraction spectra are reported. A number of transition- and post-transition-metal are chelated and collected by chitosan-glucan with higher yields than by animal chitosan. Immediate flocculation occur upon mixing chitosan-glucan dispersions with alginate and polymolybdate solutions. Membranes are also obtained from chitosan–glucan dispersions in acetic acid or in chloral and dimethyl formamide mixtures.     

Fast Inactivation in Shaker K+ Channels : Properties of Ionic and Gating Currents

Fast inactivating Shaker H4 potassium channels and nonconducting pore mutant Shaker H4 W434F channels have been used to correlate the installation and recovery of the fast inactivation of ionic current with changes in the kinetics of gating current known as “charge immobilization” (Armstrong, C.M., and F. Bezanilla. 1977. J. Gen. Physiol. 70:567–590.). Shaker H4 W434F gating currents are very similar to those of the conducting clone recorded in potassium-free solutions. This mutant channel allows the recording of the total gating charge return, even when returning from potentials that would largely inactivate conducting channels. As the depolarizing potential increased, the OFF gating currents decay phase at −90 mV return potential changed from a single fast component to at least two components, the slower requiring ∼200 ms for a full charge return. The charge immobilization onset and the ionic current decay have an identical time course. The recoveries of gating current (Shaker H4 W434F) and ionic current (Shaker H4) in 2 mM external potassium have at least two components. Both recoveries are similar at −120 and −90 mV. In contrast, at higher potentials (−70 and −50 mV), the gating charge recovers significantly more slowly than the ionic current. A model with a single inactivated state cannot account for all our data, which strongly support the existence of “parallel” inactivated states. In this model, a fraction of the charge can be recovered upon repolarization while the channel pore is occupied by the NH₂-terminus region.