Resistance to pathogens in terpene down-regulated orange fruits inversely correlates with the accumulation of D-limonene in peel oil glands

Volatile organic compounds (VOCs) are secondary metabolites acting as a language for the communication of plants with the environment. In orange fruits, the monoterpene D-limonene accumulates at very high levels in oil glands from the peel. Drastic down-regulation of D-limonene synthase gene expression in the peel of transgenic oranges harboring a D-limonene synthase transgene in antisense (AS) configuration altered the monoterpene profile in oil glands, mainly resulting in reduced accumulation of D-limonene. This led to fruit resistance against Penicillium digitatum (Pd), Xanthomonas citri subsp. citri (Xcc) and other specialized pathogens. Here, we analyze resistance to pathogens in independent AS and empty vector (EV) lines, which have low, medium or high D-limonene concentrations and show that the level of resistance is inversely related to the accumulation of D-limonene in orange peels, thus explaining the need of high D-limonene accumulation in mature oranges in nature for the efficient attraction of specialized microorganism frugivores.     

Structures similar to lipid emulsions and liposomes. Dipalmitoylphosphatidylcholine,cholesterol, Tween 20–Span 20 or Tween 80–Span 80 in aqueous media

In the present work, we show that we obtained nanometric structures made of water, 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), cholesterol (Chol), and a mixture of ethoxylated and non-ethoxylated sorbitan fatty acid esters (Tween 20, Span 20, Tween 80, and Span 80) by mixing all of them near the cloud point temperature (cp) of the ethoxylated surfactant. The influence that the constituents had on the size of the particle was determined by a pseudo-ternary phase diagram of water/Tween–Span/DPPC–Chol; the colloidal particles obtained were studied by differential scanning calorimetry, confocal fluorescence microscopy, scanning electron microscopy, and atomic force microscopy. These studies were made for all the systems with at least 23 d of colloidal stability. The most stable system was obtained with the Tween 80–Span 80 pair, behaving as a typical suspension for 48 d; this system was made of water, Tween 80–Span 80 (80:20), DPPC–Chol (95:5) in a corresponding molar ratio of 48:37:100:10. The colloidal particles obtained were a kind of emulsion and liposome structures. The second stable system was obtained with the same mixture, but in a molar ratio of 8:6:9:0, its structure was also a kind of emulsion particles. In both systems and in other less stable ones, the “emulsion particle” was completely new, it structurally corresponds to a nucleus of mixed micelles surrounded by at least one bilayer of DPPC.     

Migration timing and distance from shore of southbound eastern Pacific gray whales (Eschrichtius robustus) off Ensenada,Baja California,Mexico

Eastern Pacific gray whales were monitored off Ensenada, Mexico, during the southbound migration. The objectives were to determine southbound migration timing and width of the migration corridor during three seasons (2003–2006). Migration timing was determined by fitting a generalized additive model to the shore counts for each season and estimating the 10, 50, and 90 percentiles of the fitted curves. To estimate abundance from shore‐based counts, a probability density function for the shore based distances was estimated by a product of a gamma distribution fit to the boat survey distance data for 2006/2007 and a half‐normal detection function using combined data of the three seasons. The parameters of the gamma distribution were corrected to account for less boat survey effort carried out 20–40 km than 0–20 km from shore. The onset of the migration off Ensenada was in late December/early January and ended around 13 February. The median date was 23–26 January for the first and third season and a week early for the second season. Boat surveys indicated a wide (20 km) migration corridor but most gray whales traveled within 9.9 km from shore. The estimated total number of whales during watch hours was 2,298 (95% CI = 1,536–4,447).     

Distribution of peptidergic populations in the human dentate gyrus (Somatostatin [SOM-28, SOM-12] and Neuropeptide Y [NPY]) during postnatal development

The postnatal development of the human hippocampal formation establishes the time and place at which we start autobiographical memories. However, data concerning the maturation of the neurochemical phenotypes characteristic of interneurons in the human hippocampus are scarce. We have studied the perinatal and postnatal changes of the dentate gyrus (DG) interneuron populations at three rostrocaudal levels. Immunohistochemically identified neurons and fibers for somatostatin (SOM-12 and SOM-28) and neuropeptide Y (NPY) and the co-localization of SOM-28 and NPY were analyzed. In total, 13 cases were investigated from late pregnancy (1 case), perinatal period (6 cases), first year (1 case), early infancy (3 cases), and late infancy (2 cases). Overall, the pattern of distribution of these peptides in the DG was similar to that of the adult. The distribution of cells was charted, and the cell density (number of positive cells/mm²) was calculated. The highest density corresponded to the polymorphic cell layer and was higher at pre- and perinatal periods. At increasing ages, neuron density modifications revealed a decrease from 5 postnatal months onward. In contrast, by late infancy, two immunoreactive bands for SOM-28 and NPY in the molecular layer were much better defined. Double-immunohistochemistry showed that NPY-positive neurons co-localized with SOM-28, whereas some fibers contained only one or other of the neuropeptides. Thus, this peptidergic population, presumably inhibitory, probably has a role in DG maturation and its subsequent functional activity in memory processing.     

Salinity tolerance of three ostracode species (Crustacea:Ostracoda) of Iberian saline lakes

Laboratory experiments and field data were used to determine salinity tolerance limits of three ostracode species (Prionocypris aragonica, Eucypris mareotica and Heterocypris barbara) from Iberian saline lakes. Salinity tolerance appeared related to ionic composition and temperature. Implications for ostracode ecology and geographical distribution are evaluated.     

Nigexine, a phospholipase A2 from cobra venom with cytotoxic properties not related to esterase activity. Purification, amino acid sequence, and biological properties

The venoms of the Naja species are known to be cytotoxic. This toxicity has been attributed to the presence of small nonenzymatic polypeptides of 60 amino acid residues, designated as cardiotoxins or cytotoxins. We investigated the cytotoxic potency of Naja nigricollis venom fractions and isolated another type of cytotoxic component which is even more potent than cardiotoxins. This cytotoxic compound, which was designated as nigexine, was purified to homogeneity and its amino acid sequence was determined. Nigexine is a basic phospholipase A2 consisting of a single chain of 118 amino acids. A detailed investigation of the cytotoxic effects on epithelial FL cells, C-13T neuroblastoma cells, and promyelocytic leukemia HL 60 cells revealed that nigexine not only altered cell viability but also prevented cell proliferation. This is a property that was specific to nigexine since other phospholipases A2 from various sources had no detectable cytotoxic activity. The cytotoxic activity of nigexine was not dependent on the presence of divalent cations, unlike its enzymatic activity. In particular, the cytotoxic activity of nigexine was identical in the presence or absence of either 2 mM Ca2+ or Sr2+, or 6 mM EDTA. We also present evidence based on chemical modifications that cytotoxic activity was not correlated with enzymatic activity. Thus, modification with parabromophenacyl bromide totally abolished the enzymatic activity of nigexine, which nevertheless retained 6-20% of the cytotoxicity of native nigexine. Conversely, treatment with cyanogen bromide gave a compound that retained 7% of the enzymatic activity of the parent molecule but was devoid of detectable cytotoxicity.     

Characterization of a Cell Membrane-Associated Proteinase from Lactobacillus helveticus CRL 581

The production of a proteinase from Lactobacillus helveticus CRL 581 was studied. The highest specific activity was found at the early exponential growth phase of cells cultured in milk. The lowest levels of proteinase were detected in MRS broth, while in the casein–yeast extract–glucose broth enzyme production increased gradually during the fermentation and reached maximal values at the stationary phase. The proteinase, found to be associated with the cell membrane fraction, hydrolyzed β-casein more rapidly than α-casein. The enzyme was not released from washed cells in the presence or absence of calcium, which suggests that the enzyme did not undergo self-digestion. Received: 28 January 1997 / Accepted: 8 March 1997