Effect of diet on the lipid composition of the commercial clam Donax trunculus (Mollusca: bivalvia): sex‐related differences

This paper describes the lipid composition of the commercial bivalve Donax trunculus and the differences originated when the animals were fed with two phytoplankton species (Tetraselmis suecica and Chaetoceros sp.) in a hatchery. We also analysed sex‐related differences in lipid classes and fatty acid profile. Total lipids were higher in females than in males. Triglycerides and phospholipids were the major lipid components, and the former dominated in females and the latter in males. The main fatty acids in both sexes were 16:0, 20:5n‐3 (eicosapentaenoic acid) and 22:6n‐3 (docosahexaenoic acid). Females showed higher percentages of saturated and monounsaturated fatty acids and lower levels of polyunsaturated fatty acids than males. Significant differences in total lipid, lipid classes and fatty acid profiles were also found due to diet. Docosahexaenoic acid decreased and total lipids, free fatty acids, arachidonic acid and EPA increased in both sexes. Despite these differences, the condition of the species was maintained and the broodstock even maturated.     

Induction of variability in chimeric Aster cordifolius `White Elegans' through somaclonal variation

A protocol was developed for plant regeneration from leaf explants (laminaand petiole) of Aster cordifolius cultivar `White Elegans', which ischimeric for chromosome number and the ligulate flower colour. Explantswere cultured on MS or Gamborg's B5 medium in presence of IAA, 2,4-Dand BAP, alone or in combination. The highest frequency of shootregeneration was obtained on B5 medium supplemented with 2,4-D(0.09 mg l^-1) and BAP (1.8 mg l^-1). After the invitro rooting stage and acclimatization, 90% of plantlets survived in thegreenhouse. The regeneration process occurred by indirect organogenesisas shown by cyto-histology. The regenerants maintained the originalchimerism for chromosome number. Pink flowers instead of theexpected white ones were obtained in all regenerants. Ahypothesis for the uniform colour change is discussed. Variations weredetected in the regenerant generation (R₀) for quantitative characterssuch as capitulum and disc diameters, and number of ligulate flowers. SinceAster can be vegetatively propagated, selection of variants in R₀can provide interesting material for breeding purposes.     

Cadmium Effects in Sunflower: Membrane Permeability and Changes in Catalase and Peroxidase Activity in Leaves and Calluses

Mechanisms preventing oxidative burst in cells exposed to high metal concentrations are crucial for cell survival. In this report, sunflower (Helianthus annuus L.) was used as a model species to investigate: (a) how cadmium (Cd) affects plant defense pathways (in particular, those involved in preventing oxidative stress), and (b) whether antioxidative enzymes of plants and of in vitro cell culture (calluses) have similar responses to Cd exposure. For this experiment, plants (grown hydroponically on Long Ashton medium) and calluses (grown on Murashige and Skoog medium) were exposed for three weeks to different Cd concentrations (0, 5, 50, and 500 μ M). Solute and electrolyte leakage increased significantly with the increase in Cd concentration in the external medium and in exposed leaves, and less in exposed calluses. Cadmium exposure also reduced significantly soluble protein contents in both leaves and calluses. The activities of catalase and peroxidase decreased significantly in 50 and 500 μ M-exposed leaves compared with the control, but increased in 5 μ M-exposed calluses, decreasing in the calluses exposed 500 μ M Cd. The decrease in antioxidative enzymes activities is congruent with the decrease in membrane integrity and suggests that calluses develop antioxidant mechanisms that respond better to Cd stress than do leaves. On average, 100% of plants exposed for 21 d to 500 μ M and 95% of plants exposed for 45 d to 50 μ M Cd were dead. After 45 d, only 53% of 50 μ M-exposed calluses had died. These surviving calluses were maintained on 50 μ M for six months. Six-month-old exposed calluses had higher activities of peroxidase and catalase when compared with control calluses, as well as lower membrane degradation. These data show that calluses are more tolerant than plants to Cd exposure, and that antioxidant mechanisms under Cd exposure may differ between the two cell systems and vary with time.     

Novel approach to study oxidative stability of extra virgin olive oils: importance of alpha-tocopherol concentration

The stability of extra virgin olive oils is mainly due to their relatively low fatty acids unsaturation and to the antioxidant activity of some of the unsaponifiable components. We studied the activity of alpha-tocopherol in extra virgin olive oil in its natural state, using new and simple oxidizing conditions in "thin layer" and "bulk phase". Oxidation time course was monitored at 37 degrees C or 75 degrees C. A storage test was also performed. Two parameters were evaluated: depletion of alpha-tocopherol and formation of PUFA hydroperoxides, measured as conjugated dienes (CD) and peroxide value. The value of complex polyphenols was also measured. alpha-Tocopherol concentration decreased in function of time and temperature and showed a strong inverse correlation with the increase of CD. When alpha-tocopherol reached a "threshold value" of 60-70 mg/kg, a significant increase of CD formation was observed, together with a good correlation between CD and peroxide value. The initial amount of alpha-tocopherol is one of the components that influences oil oxidative susceptibility.     

Characterization of sphingolipids from sunflower seeds with altered fatty acid composition

Sphingolipids are a group of lipids that are derived from long-chain 1,3-dihydroxy-2-amino bases and that are involved in important processes in plants. Long-chain bases are usually found bound to long-chain fatty acids forming ceramides, the lipophilic moiety of the most common sphingolipid classes found in plant tissues: glucosyl-ceramides and glucosyl inositol phosphoryl-ceramides (GIPCs). The developing sunflower seed kernel is a tissue rich in sphingolipids, although, importantly, its glycerolipid composition can vary if some steps of the fatty acid synthesis are altered. Here, the sphingolipid composition of the seed from different sunflower mutants with altered fatty acid compositions was studied. The long-chain base composition and content were analyzed, and it was found to be similar in all of the mutants studied. The sphingolipid species were also determined by mass spectrometry, and some differences were found in highly saturated sunflower mutants, which contained higher levels of GIPC, ceramides, and hydroxyl-ceramides.     

Biotechnological production of vitamin B2-enriched bread and pasta

Lactic acid bacteria (LAB) were obtained from durum wheat flour samples and screened for roseoflavin-resistant variants to isolate natural riboflavin-overproducing strains. Two riboflavin-overproducing strains of Lactobacillus plantarum isolated as described above were used for the preparation of bread (by means of sourdough fermentation) and pasta (using a prefermentation step) to enhance their vitamin B2 content. Pasta was produced from a monovarietal semolina obtained from the durum wheat cultivar PR22D89 and, for experimental purposes, from a commercial remilled semolina. Several samples were collected during the pasta-making process (dough, extruded, dried, and cooked pasta) and tested for their riboflavin content by a high-performance liquid chromatography method. The applied approaches resulted in a considerable increase of vitamin B2 content (about 2- and 3-fold increases in pasta and bread, respectively), thus representing a convenient and efficient food-grade biotechnological application for the production of vitamin B2-enriched bread and pasta. This methodology may be extended to a wide range of cereal-based foods, feed, and beverages. Additionally, this work exemplifies the production of a functional food by a novel biotechnological exploitation of LAB in pasta-making.     

Increasing resistance to Fusarium crown and root rot in asparagus by gametophyte selection

In garden asparagus, Fusarium crown and root rot is the main cause of crop decline. Since chemical treatments are inefficient, efforts should focus on the development of resistant cultivars to control the disease. Toxic culture filtrate (TCF) of F. oxysporum has affected asparagus pollen germination and tube growth. Consequently, gametophyte selection was evaluated to ascertain if the application of selective agents at this level could increase selection efficiency. Two susceptible pistillate plants and one tolerant and one susceptible staminate plants were used in controlled crosses. Before pollination, a drop of a germination vehicle with TCF or without it was applied to the stigmas. Some pollinated pistils were fixed and analyzed by fluorescence microscopy; the rest were left on the plant for seed production. Fifty to 200 seeds were obtained per treatment combination (staminate plant x pistillate plant x pollination vehicle). The derived plantlets were inoculated in vitroand evaluated for disease symptoms. The application of TCF to stigmas reduced pollen germination and tube growth compared with untreated controls,regardless of the genotypic combination. Pollen germination and tube growth was poorer for the tolerant staminate genotype than for the susceptible one. When the TCF was applied, the number of seeds per pollination in comparison with the controls diminished only when the susceptible genotype was the pollinator. The percentage of affected root area of the progenies obtained after applying the TCF was lower than in the controls only when the tolerant genotype was the pollinator. Increasing Fusarium resistance in asparagus by means of gametophyte selection seems feasible. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hormonal effects on ontogeny of swimming ability in the rat: assessment of central nervous system development

The maturation of swimming behavior and the evoked cortical response to sciatic stimulation were studied in newborn rats receiving thyroxine or cortisol. Compared to that of controls the maturation of swimming is accelerated or delayed 2 to 3 days by thyroxine or cortisol treatment, respectively, and this corresponds to ontogenetic shifts in the characteristics of the evoked potential. Front leg movement during swimming normally diminishes at about 16 days of age and is inhibited by day 22. Thyroxine also advances and cortisol delays the age at which this inhibitory mechanism becomes evident, and compresses (thyroxine) or expands (cortisol) the time interval over which it becomes functional. During early postnatal life certain circuilating hormones can affect the rate and chronology of central nervous system maturation. Swimming behavior may be a simple model to use in studies concerned with factors affecting the functional and behavioral development of the central nervouts system.