Effects of oxygen level on metabolism and development of seedlings of Trapa natans and two ecologically related species

Seeds of the water plant Trapa natans L. (water chestnut) can germinate in strict anoxia. The seedlings show seminal roots growing upwards while shoot buds remain quiescent until O₂ becomes available. Trapa seedlings are highly tolerant to anoxia. The rate of ethanol fermentation was 21.2 μmol (g FW)⁻¹ h⁻¹, while production of lactate was negligible and lower than that of succinate. The seminal root of Trapa compares better to the rice coleoptile rather than to the rice root, both functionally and as to the metabolic response to anoxia. The anaerobic germination of Nuphar luteum L. and Scirpus mucronatus L. was also characterized by a limited developmental program.     

A NEW PHYLOGENY FOR CHROMOPHYTE ALGAE USING 16S-LIKE RRNA SEQUENCES FROM MALLOMONAS PAPILLOSA (SYNUROPHYCEAE) AND TRIBONEMA AEQUALE (XANTHOPHYCEAE)1

The 16S-like ribosomal RNA genes from Mallomonas papillosa Harris et Bradley (Synurophyceae) and Tribonema aequale Pascher (Xanthophyceae) were sequenced and compared to those of other eukaryotes. Mallomonas is closely related to Ochromonas (Chrysophyceae) and supports the general hypothesis of a close phylogenetic relationship between the Synurophyceae and Chrysophyceae. Tribonema is specifically related to Costaria costata (C. A. Agardh) Saunders (Phaeophyceae) demonstrating an unexpected phylogenetic relationship between the Xanthophyceae and Phaeophyceae. Distance and parsimony analysis place these four chromophyte genera in a complex evolutionary assemblage that includes the Bacillariophyceae and Oomycetes but excludes the Dinophyceae. The close relationship between the chromophyte algae and the Öomycete fungi supports the hypothesis that protists with tripartite hairs form a natural assemblage.     

Effects of organic amines on α-aminoisobutyric acid uptake into the vacuole and on ethylene production by tomato pericarp slices

Experiments were conducted to test the possibility that organic amines inhibit ethylene production by inhibiting transport of the ethylene precursor, 1-aminocyclopro-pane-1-carboxylic acid (ACC), into the vacuole. α-Aminoisobutyric acid (αAIB) was used as a model substrate to study ACC uptake into the vacuole in relationship to ethylene production in pericarp slices of Lycopersicon esculentum Mill. cv. Liberty treated with and without organic amines and related substances. Organic amines (polyamines and other basic amines) inhibited αAIB uptake into the vacuole. These amines also enhanced ACC accumulation in the tissue and reduced the passive efflux of αAIB from the vacuole. Overall, ethylene production was inhibited. The inhibition of αAIB transport and of ethylene production followed a polyvalent cationic progression in the order polyamines > diamines> basic 1-amino acids. Ca²⁺, but not Mg²⁺, strongly stimulated αAIB uptake into the vacuole and ethylene production. At equal concentrations, Ca²⁺ counteracted the inhibitory effects of polyamines on both αAIB uptake and ethylene production. Competitive and irreversible inhibitors of polyamine biosynthesis stimulated αAIB uptake into the vacuole and ethylene production. The results indicate an apparent relationship between polyamines, ACC uptake into the vacuole and ethylene production.     

The anti-platelet approach targeting the fibrinogen ligand of the GPIIB/IIIa receptor.

Activation of the platelet surface receptor GPIIb/IIIa is the final pathway of platelet aggregation, regardless of the initiating stimulus. RGD analogues, peptidomimetics and monoclonal antibodies to GPIIb/IIIa have been developed targeting the blockage of the receptor and inhibition of the fibrinogen binding. However, the intrinsic activating effect of GPIIb/IIIa blockers is widely discussed as one potential contributing factor for the disappointing outcome of trials with GPIIb/IIIa inhibitors. An alternative method for thrombus prevention could be the use of specific fibrinogen blockers since they will act at the final step of the platelet aggregation and are expected to leave the receptor unaffected. To achieve this target the design of the fibrinogen ligands could be based on (i) sequences derived from GPIIb/IIIa ligand binding sites, and (ii) sequences complementary to RGD and/or to fibrinogen gamma-chain. The available information, which could be used as a starting point for developing potent fibrinogen ligands, is reviewed.     

First chemical synthesis of a scorpion alpha-toxin affecting sodium channels: the Aah I toxin of Androctonus australis hector.

Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time.     

CYTOCHROME P450 1A1 EXPRESSION IN CETACEAN INTEGUMENT: IMPLICATIONS FOR DETECTING CONTAMINANT EXPOSURE AND EFFECTS

Contaminant related health risks to marine mammals are typically inferred from the levels of contaminants measured in blubber. Such measurements alone are insufficient to indicate the likelihood of biological effects from contaminant exposure, especially for contaminants that do not bioaccumulate. Cytochrome P450 1A1 (CYP1A1) in mammals is induced by, and involved in, the metabolism of planar halogenated aromatic hydrocarbons and polycyclic aromatic hydrocarbons, chemicals of concern in aquatic systems. CYP1A induction is a molecular response to exposure to these inducers in many vertebrates. Using immunohistochemistry, we semiquantitatively measured CYP1A1 expression in integument (epidermis and blubber) collected by biopsy or at necropsy from 17 species of cetaceans. CYP1A1 expression was detected in all species and, in some cases, varied both within and between species. CYP1A1 expression in mysticetes was comparable to that in odontocetes. Assessing how the differences in contaminant burdens, life history parameters, and physiological condition between individuals, populations, or species affect CYP1A1 expression in cetacean integument is essential to the interpretation of this induction as a biomarker of exposure to and effects of contaminants. Detection of CYP1A1 expression in integument samples offers a relatively simple, non-lethal technique to study biological changes associated with contaminant exposure in cetaceans.